Creating Multiple Excel worksheets in a workbook from an SQLserver 2008 table

Question: This is my first time on this forum.  I will do my best to describe my question.
I have a table in my database called SerialExtract that has 4 fields.   Productnumber, serialnumber, Constraint, Volume.   What I need to do for my customer is load this data into an Excel workbook - where there is a tab (worksheet) for each Productnumber in my table, and the associated data for that product on that tab.   The tabs need to be dynamic (since the productnumbers will change) - so that each time I run the load it refreshes the excel workbook.
Any suggestions on what type of tool I should use to accomplish this?   My initial thoughts were to use SSIS or write a SPROC in SqlServer that can write to the Excel workbook.  I can loop through the data by product - just not sure how to write to Excel with different tabs based on data.
thanks!
Barb
Answer: In Excel, there is a built-in feature to query data from a SQL server and to get the data loaded into an Excel spreadsheet. Side note, you can do this dynamic connection from various external sources, not only for SQL Server.
Simply use this feature by defining this query in each spreadsheet of your workbook. Here is a screenshot where you can find the option in Excel 2010.


Is there a political term for a strong (democratic) state that has much influence in contrast to a weak one?

Question: Some political parties (ie economic liberalism) want a "weak" state that has less influence, other seek a strong one.
Is there a term that describes a (democratic) state that is a strong one?
Comment: Informal term is "big government" (as opposed to "small government"). I'm not sure if this is too informal to answer the question for you.
Answer: A popular political direction which favors a big government dedicated to upholding democratic ideals like liberty and equality is social democracy. The systems of many European states are often described that way. An even stronger form which hasn't seen much use in the real world yet is democratic socialism.
The main difference between these two ideologies is that social-democrats consider free markets a tool which can be used to solve many (but not all) problems, while democratic socialists consider a state-controlled planned economy to be inherently superior to a free market economy. Both differ from pure socialism in that they want to bring and govern their respective systems in a democratic manner and not enforced through an autocratic government.
Answer: Misread the question (thought it was about what is covered in weak government political theories).  But thought I'd outline the Small Government models (As opposed to Big Government, which @Philip covered).  As asked "Big Government" is the term for a Government that is stronger and often more centralized.  Small Government encompasses a lot of different ideas characterized by a weak central government with a more powerful regional government.  These terms are more common to governments with Strong Federalism (i.e. a bunch of small nations decide to collectively cede power to form a large one) and tend to form around what the highest level of government can do with respect to the law and the lower levels of government.  Generally opponents of Big Government believe that the Government is not the solver of all societal problems and that it might fall to a lower level of government authority OR a private cooperation that can make innovative changes faster than the government can.  Proponents of Big Government believe that the higher level of government can leverage more resources than the lower level and should act in situations where the lower level government is too weak to act (either the will of the people is preventing important social changes or regulations on big industries).  These are lose definitions and are not all favored by people (Big Government is a bit more pejorative as it gives the idea of a soulless giant monster ala Big Industry, Big Medicine, Big Oil) so the term is rarely used by people who support it.
In the United States, this system of Government is called a Jeffersonian Democracy, which favors a weak centralized government (without writing tons, a Jeffersonian believes the Local Government should have more control over an individual by law as they are easier for the individual to fight) and as the scope of authority rises in a federal system, the government deals less and less with the individual and more and more with lower governments.  This is mostly academic.  The Crux of all U.S. Politics is Jeffersonian Democracy (American Conservatism) vs. Jeffersonian Democracy combined with Jacksonian Democracy (basically, more government roles should be decided by popular vote.  This belief is such an integral part of the Democrat party, that until recently, they would have a big "holiday" celebrating the two individuals with a fund raising dinner.  These are no longer popular as Jefferson was a slave owner and Jackson committed illegal genocide against Native Americans.  Still their ideas on government are popular...).
Constitutional Republics (especially those that used the U.S. Constitution in part or wholesale as a Constitution model) are governments where the highest law of the land are laws that restrict the government (in the U.S. the government is the only legal entity that can commit illegal offenses against the constitution).  All democracies in the world are Constitutional save for the UK and New Zealand, which are Parliamentary (the legislature makes the ultimate law) (Australia may qualify as they have Constitutional Law, but not defined by one document), though the level of restrictions may vary between country.
Classical Liberalism (in the European sense) are the ideas that the American Founding Fathers founded the United States on.  NeoLiberalism is an offshoot of that, which tends to favor Economically Liberal (European Sense.  They are Conservative in the United States) and Socially Progressive policies.
Libertarianism (especially in the United States) is the idea that a government should be concerned about protecting the rights of an individual from abuse by other individuals (or government) but the range of individual agreements is set by the two individuals (i.e. there is a contract between two individuals that includes a morally offensive act.  It is valid if both parties understand the terms of the agreement and willfully accept them.  The government should not interfere unless the terms not fairly represented.  I.E.  The government should not interfere in the sale of an immoral substance unless the price for transaction was not payed by one of the parties.  The Government has no right in preempting the contract by making the sale of the substance illegal.) (American Libertarians tend to be closer to political conservatives, but they greatly divide on military spending).
Anarchy abolishes all government and makes the enforcement of individual rights the duty of other individuals (also a pure/direct democracy does this.  Basically "Democracy is two wolves and a sheep deciding what's for lunch.").
Apologies for the America-centric nature of this and switching between terms (I tried to explain which terms are related to which geographic area).  American Politics have historically been between Big Government (The Federal Government) and Small Government (States and/or local level), so the ideas encompass their own terms a lot.  In fact, a 2013 Pew Research Poll found that 54% of Americans believe their government does too many things as is.
As with all political terms, this one tends to get defined under a lot of different ways.  Just how much government is too much verses what to cut to shrink government is not agreed upon among small government circles.  Often it is seen as a good thing to fight the government on any grabs for more power as it is harder to take it back once government does get it.


How to solve the differential equation $xx'' = (x')^2$?

Question: There is an differential given:
$$xx'' = (x')^2,$$
where $x' \neq 0.$
I tried to solve this problem but I cannot see the proper substitution.
Comment: $(x/x')'=((x')^2-xx'')/(x')^2$ may help.
Comment: Worth noting the next time you see a problem like this is that the closed-form solutions to second-degree differential equations of one variable often involve $c_1 \sin k_1 x + c_2 \cos k_2 x$, as the first and second derivatives have the same form. The $\sinh$ and $\cosh$ functions also often appear, for similar reasons.
Answer: Think that
$$
\frac{\ddot x}{\dot x} = \frac{\dot x}{x}\Rightarrow \frac{d}{dt}\ln(\dot x) = \frac{d}{dt}\ln (x)
$$
so
$$
\ln(\dot x) = \ln(x) + C \Rightarrow \dot x = C_1 x\Rightarrow x = C_2e^{C_1 t}
$$
Comment: Thanks LutzL for the hint.
Answer: The comment seen here uses a "trick". Here is a more standard solution.
The independent variable is not rendered explicitly so you have an autonomous equation.  Given this, put in $u=x'$.  Then
$$x''=\frac{d}{dt}u(x(t))=\frac{du}{dx}\, x'=u\,\frac{du}{dx}$$
using the Chain Rule.  So
$$x\cdot u\cdot \frac{du}{dx}=u^2$$
Divide by $u$ and solve the separable equation that results, then substitute $x'$ for $u$ into that first integration to get another first order equation that is easily solved.
Comment: Agreed.  Ironically, the solution gotten by assuming $u\ne 0$ also covers $u=0$ given the proper value of one integration constant.  Dumb luck strikes again!
Comment: Which works in this case because $u = x' \neq 0$.
Answer: With the substitution $$v(x)=\frac{dx}{dt},$$ we get
$$x\frac{dv(x)}{dx}v(x)=(v(x))^2.$$
This can be written as
$$-v(x)\left(-x\frac{dv(x)}{dx}+v(x)\right)=0,$$
so either $v(x)=0$ or
$$\frac{dv(x)}{dx}=\frac{v(x)}{x}$$ and this is
$$\int\frac{\frac{dv(x)}{dx}}{v(x)}dx=\int\frac{1}{x}dx.$$
Can you finish?
Answer: $$xx'' = (x')^2,$$
Divide by $x^2 \,\, x\neq 0)$
$$\frac {x''}x = \frac {(x')^2}{x^2}$$
Note that
$$(\frac {x'}x)'= \frac {x''}x-\frac {x'^2}{x^2}$$
Therefore
$$\frac {x''}x = \frac {(x')^2}{x^2} \implies (\frac {x'}x)' =0$$
$$\frac {x'}x =K_1 \implies \ln|x|=K_1t+K_2 \implies x=K_2e^{K_1t} $$


Is roasting a whole duck something a beginner should avioid?

Question: I have experience in my own kitchen and I can follow a recipe. I was planning on serving roasted long island duck for a Christmas party for about 8-10 people.
Comment: Also, it's never a good idea to cook a dish for the first time for guests. Always practice first!
Comment: Heck, I'd do a practice round just to have more duck all to myself.
Comment: This would be a lot more useful if you instead asked what can go wrong and how to avoid it.
Comment: One advice I would give is to cut the duck and cook it's different parts in a pan, instead of roasting it, especially if you don't feel confident enough. Then you cook it like chicken without the minimum temperature constraint (duck can can rare/medum/well done).
Comment: I would definitely recommend at least spatchcocking the duck it make it easier. Don't be afraid to experiment, you don't learn anything without trying. But as ElendilTheTall said I would do a practice run first.
Answer: What I learnt from my neighbor:
The most critical part also the most enjoyable part for the diners is to make the skin crispy. For this many factors should be taken into consideration (e.g. the type of oven you use, room temperature where the oven is, etc).
But the trick for the skin to be crispy is how much the skin can become detached from the meat while it is cooked, thus a layer of heat remains between the skin and the meat.
This is what I learnt:
From the inside of the duck, carefully poke holes with a toothpick through the meat but not breaking the skin.
Second, use a pan where there are holes on the bottom and place another pan directly underneath it to collect the fat / oil while the duck is being cooked.
At the very end, take the duck out of the oven and quickly turn up the oven to even higher temperature.
Once the oven has reached the higher temperature, pour evenly the collected fat / oil on top of the duck and put it right back to the oven and let it cook shortly.
The result is the skin will be very crispy and with you taking out the duck at the last step while the oven's temperature is turned up higher, the duck will not be over-cooked.
Answer: See my relevant answer to a related question.  In short, I would recommend avoiding roasting a duck whole—regardless of your skill level, and especially if you are a beginner.  The only two advantages you get from roasting the bird whole are the theatrics of tableside presentation and also ease of preparation (i.e., you don't have to worry about butchering the bird).  If you aren't going to be carving the bird tableside, then then there really isn't any gustatory advantage to roasting the bird whole.  As others have mentioned, it is exceedingly hard to ensure that the skin is perfectly crispy and all of the various muscles are cooked to their ideal temperatures when roasting the bird whole.
Answer: I consider myself a beginner, and I would not be comfortable trying to cook a duck. When done right, duck is one of the most wonderful foods. When done wrong, it is horrible.
I consider duck a challenging meat because it is best served rare. However, you really should have the skin crispy. That takes some very precise timing to have the muscle rare but successfully crisp the skin.


Understanding Monodromy by examples

Question: What is the intuition behind "monodromy"? Could you explain with some examples?
For instance, what does it mean "monodromy around a singular fiber is a dehn twist"
I don't understand what it means pictorially.
Comment: Have you tried wikipedia or the online encyclopedia of mathematics? Also, maybe this is helpful: http://math.berkeley.edu/~auroux/277F09/L9.pdf
Comment: @PiotrAchinger yes, I read the definitions out there, but still It's not clear to me. Thanks though!
Comment: How can we possibly help you if you don't tell us where you got lost?
Answer: I would take a step back and look at the root of monodromy (many math terms can be better understood when looking at their meaning from a Latin / Greek perspective).  In this sense, monodromy means ``running round singly''.
But what does that tell us in a mathematical perspective?  In essence, this is nothing more than running around a singularity, or more precisely, a ramification point (that is when we consider the pull-back, we are looking at some branchpoint where a bunch of fibers are being pinched together).
We want to understand the type of action that is occurring when we circle a ramification point.  If we consider a homotopy that moves around the ramification point and consider the lifting of this homotopy on our fibers, we see then that monodromy permutes where we land on our fibers as we move around the ramification point.
Consider the following example.
$f(x) = x^2 + t$.  For generic values of $t$, we have $2$ solutions, but at $t = 0$, we have a ramification point.
Let's just say $t = 1$.  So, now we have the system $f(x) = x^2 + 1$, which has two solutions $\pm i$.  Let's consider the positive solution, $i$.  Now, let's construct a homotopy that circles around our ramification point of $t = 0$, parametrized by $e^{i\tau}$, for $\tau = 0$ to $2\pi$.  After one `loop', we have that our positive solution at $i$ gets permuted to the negative solution at $-i$.  Circling around again, we see that the action becomes closed and we return to our original point.
A singular fiber (or how I can best understand what is being meant by this) is a branchpoint, i.e. some point in the pull-back where the generic number of solutions is deficient.
In the sense of a dehn twist, when you look at the lifting of the homotopy along the particular fiber that it is tracking is the dehn twist, i.e. the path that you follow when you swap fibers as you move around the branch point.  Note that the projection of the dehn twist is precisely the circle that is parametrized by the homotopy that circles around the ramification point.
I hope this helps.
Comment: Makes sense, totally! Could you explain why "monodromy around a singular fiber is a dehn twist" in the same sense?
Answer:
A Dehn twist is an operation so we need a before an after. In the picture below imagine the top and bottom of each cylinder are identified so that the end points of the red curve are identified, the end points of the blue curve are identified, and there is no twisting of the red curve on the left, e.g the red and blue curves are unlinked.
Here is my guess at what is meant by "monodromy around a singular fiber is a dehn twist". I'll admit I am guessing here a little because I don't have the full context.
The Dehn twist operation will be to take the red curve and replace a neighborhood of it near the green curve with a curve that goes once around the cylinder. The singular fiber is meant to be blue. If we consider the two curves parallel and unlinked on the left, then on the right the linking number of the red and blue curves is 1, i.e the red curve goes once around the singular fiber.
Answer: The simplest situation is when your fibration is actually a covering space and the simplest nontrivial covering space is given by $f: S^1\to S^1$ where $f(z)=z^2$. Roughly speaking this map wraps the upstairs (domain) circle around the downstairs (target) circle twice. If you start from any point downstairs and make a full rotation, the corresponding point upstairs makes a half rotation whicn is the same thing as the effect of the antipodal map. So, one says that the monodromy of this fibration equals the antipodal map!
Now note that you can extend $f$ to a singular fibration from the complex plane to itself where the singularity is the origin. This can give you an intuition as why the monodromy around a singular fiber should be a Dehn twist: The Dehn twist around a circle is the antipodal map when restricted to the circle itself.
Warning: If your fibration is not a Lefschetz fibration (locally given around a singularity by $f(z_1,...z_n)=z_1^2+..+.z_n^2$ then its monodromy around a singularity may not be a Dehn twist.
Answer: A general result along that by @Reza that may be of interest to some:
If a 4- manifold admits a genus -g fibration ; $ g \geq 2 $, then it admits a Symplectic structure. See theorem in p.5 of https://www.csun.edu/~tf54692/N16-lf.pdf

Understanding Monodromy by examples


FTP installation of WordPress

Question: The client am working with want a website built and I discovered the site use for hosting. The problem I am having is that they want a WordPress site.  What I am used to is installing WordPress of the domain in question and then start developing. But in this case they only want to provide a FTP login. Wouldn't they still have to provide the cpanel login information so I can install WordPress using this hosting provider or should I ask them to install a WordPress and provide you the WordPress admin login details?
Answer: FTP login is more than enough to install wordpress. You just need to upload your wordpress's root folder content (not root folder itself) via FTP and then open your site's admin section via browser something like this http://www.yoursite.com/wp-admin/. Then you will see wordpress installation step. Follow that steps and your wordpress installation is done.
NOTE If you are uploading wordpress from local or from other domain (not fresh setup) then don't forget to change database name, username, password, host in wp_config.php available in root folder of wordpress.
Following steps must be done only after you have a database ready to install wordpress because on installation you need to specify database name, username and password. And database can't be created with FTP.
Comment: If you have done installation in local then you don't need to worry because Installing in local or installing via FTP is same. Like we place wordpress folder in `httpdocs` in local then we open url (`localhost/site/wp-admin`), same goes to FTP. Upload and open site url (`ursite.com/wp-admin`). There is no extra step in installing via FTP than local.
Comment: that is actually not true, you need access to cpanel to create the DB if it is not created yet
Comment: So once I use FTP to install it, I'll have the regular login, is that what you're saying?
Comment: @Mark Kaplun Yes ofcourse a database is required. I have already mentioned in **NOTE** in my answer to change name of DB. In my answer I have shown only FTP's way of installation but for database creation access of `phpmyadmin` is required.
Answer: Yes, installing wordpress via the hosting admin with a one click install is both faster and less error pron. It also give the hosting company a chance to deploy whatever optimizations they might have for wordpress on their servers.
In any case you will need access to "cpanel" to create the DB.
Answer: FTP is enough (and frankly, preferred) to install wordpress. It's only a couple steps, and there are a million resources online to walk you through it. Here's one.
You don't need cpanel access to do the install, but you WILL need credentials for a few services. If the client cannot provide those credentials, they may wish to give you cpanel access instead.
Requirements

FTP username and password
MySQL host, username and password
MySQL database created for wordpress
Access to phpmyadmin would be ideal, but not required

If your client can't provide that, gently offer to help by either walking them through it on the phone, or getting access to take care of it yourself.
Simply upload all the unzipped files to the web root directory (this depends on your host. It may be ~/public_html, or ~/web, or something else). Then point your browser to the domain, and the wordpress install script will guide you through the setup.
As for your other question: once you install wordpress, you'll be given a username and password to login to wp-admin. That's all you'll need to setup everything on the backend.
Good luck!

FTP installation of WordPress


Will my lasagna be ruined because I forgot to put the white sauce on the lasagna sheets

Question: I was making lasagna and put in the meat and the lasagna sheets but then I realized (after I had finish the layers and the cheese top), I forgot to put the white sauce on top of each layer of lasagna sheets, will this ruin the lasagna?
Comment: Hi, and welcome to SA! Have a look at the [Tour](https://cooking.stackexchange.com/tour) and [Help Center](https://cooking.stackexchange.com/help) when you get a chance. The answer to this question will depend on what you consider 'ruined'; in general it is always helpful if you could share the recipe you used.
Answer: No.
Anecdotal, I rarely use white sauce in lasagna and it always rocks.
Comment: Might be worth adding that you need enough moisture in your meat/bolognese for the lasagna sheets to cook properly and not become dried up sheets of rock.


How can I keep track previous server's activities?

Question: I would like to keep track the server activities (e.g last night) within a specific time range, any tool or method recommended? thank you.
Comment: Please specify what type of server, and what type of activities you want to know about.
Comment: You must be *SUBSTANTIALLY* more specific with your question: What do you want to know? You could put a video camera in front of the box and get information on "activities" ("The server sat there all night, blinking its lights"), but that would hardly be useful :-)
Answer: the only time-stamped info I can think of would be logs: /var/log/syslog, /var/log/apache2/access.log, and the like. login info would be viewable more readily using last or lastlog. $HOME/.bash_history for each user can show non-timestamped data; check the ctime and mtime to see when the inode or data was last updated.

of course, all that stuff is unreliable if anyone besides you has root access; everything is capable of being erased and/or edited.
Answer: If your looking on a network level you could try nagios, a nice open source monitoring tool, you can create custom scripts to monitor specific aspects as well check port availability, server uptime etc.. information can be presented in graph and diagram format.
There is a plugin specifically to monitor between certain servers between certain times.
Answer: If your server is a web server, and you want to track visitors' pattern, you can try Google Analytics. It is free & powerful.


How does one find who or what (service) deleted a particular file or folder in Solaris?

Question: Is there any tool or logs which could give information about it? Also, if there is no way to find out the above then... can I do something which informs me when someone or some service tried to delete the folder.
Answer: AFAIK there is no "out the box" solution but you could use an event driven file watcher for file system events (on the directory its in) - then look up the offending program(s) that match the handle.
If you need such an application then it may be worth asking on StackOverflow as you cannot be the only with such a need.
Comment: StackOverflow is only appropriate if you intend to write such an application yourself
Answer: This small Dtrace script will easily log every file deletion in the system:
<code>dtrace -qn 'syscall::unlink*:entry { printf("%d, %s, %s\n", uid, execname, copyinstr(arg0));}
syscall::fsat:entry  /arg0 == 5 / { printf("%d, %s, %s\n", uid, execname, copyinstr(arg2));}'
</code>


Disk Capacity Planning for Whisper / Graphite

Question: Does anyone have any formulas, or maybe some sample data from their environment that can help me estimate how much disk space will be used by graphite per datapoint?
Comment: Make sure you're planning your disk I/O correctly too, and not just your disk capacity. rrdtool has, over the years, accumulated a lot of micro-optimizations that make it a lot faster (2x faster?) on writes than Graphite's Whisper database format. If you're planning on keeping all your data on decent SSD, that will get you most of the way there, but I wouldn't plan to keep a whole ton of Whisper DBs on spinning disk. At scale, it's just not cost-effective that the disk I/O levels that Graphite throws.
Answer: whisper-info.py gives you a lot of insight into what and how each file is aggregated, including the file's size.
However it's only useful for existing whisper files.
When you want to see predictive sizing of a schema before putting it in place, try a Whisper Calculator, such as the one available at https://gist.github.com/jjmaestro/5774063
EDIT:
When asked for an example...
storage_schema:
{
    :catchall => {
      :priority   => "100",
      :pattern    => "^\.*",
      :retentions => "1m:31d,15m:1y,1h:5y"
    }
}

Looking at my file applied-in-last-hour.wsp, ls -l yields
-rwxr-xr-x 1 root root 4415092 Sep 16 08:26 applied-in-last-hour.wsp

and whisper-info.py ./applied-in-last-hour.wsp yields
maxRetention: 157680000
xFilesFactor: 0.300000011921
aggregationMethod: average
fileSize: 4415092

Archive 0
retention: 604800
secondsPerPoint: 10
points: 60480
size: 725760
offset: 52

Archive 1
retention: 2678400
secondsPerPoint: 60
points: 44640
size: 535680
offset: 725812

Archive 2
retention: 157680000
secondsPerPoint: 600
points: 262800
size: 3153600
offset: 1261492

So, basically you combine your hosts per retention-match per retention-period-segment per stat, multiply by a factor of systems that you intend to apply this too, factor in the number of new stats that you're going to track.  Then you take whatever amount of storage that is and  at least double it (because we're buying storage, and we know we'll use it...)
Comment: Any chance you have some sample numbers from that (paired with retention settings). Right now I'm thinking about different time series data stores in terms of disk usage - so getting graphite live for that is bit a of a todo.
Comment: @KyleBrandt Answer updated.
Comment: Thanks for this. So with the filesize, is that what it will be after an hour of collecting data, or is that what the filesize will pretty much always be? So is 4415092 representative of 5 years worth of data this retention, or is that representative of one hour of 1 minute data? Also, is that bytes or bits?
Comment: This is a new implementation at this company, and I don't have access to my old one.  Since the top-level fileSize result matches the `ls -l` result, I take that to be bytes. When I add up the sizes of the archives within the .wsp file (as reported by `whisper-info.py`), they come close to the overall .wsp file size (the rest I assume being metadata and such. This should be the size of the file for all time, as data falls down to lower data resolutions, and old data points are discarded.
Comment: Okay, so with this retention settings. Roughly: `ServerCount * MetricCount * 4.5MBytes`
Comment: You have to calculate this for every retention policy, and 4.5MB is what it works out to for my (single) retention policy, but yes, that's the rough formula...
Comment: Really the simplest thing is to just try it. Set a retention policy, send in some data, and then use "ls -l" to see the file sizes. Whisper (.wsp) files NEVER change in size. Once created with one storage scheme, they never change. Delete them, change the schema, try it again. Check file sizes. This is a fast process. Do some simple multiplication then based on your number of data sources, and you are done. No need for formulas.
Comment: Really, the simplest thing to do is use a Whisper Calculator tool, such as the one at https://gist.github.com/jjmaestro/5774063
Answer: In the documentation for statsd they give an example for a data retention policy.
The retentions are 10s:6h,1min:7d,10min:5y which is 2160 + 10080 + 262800 = 275040 data points and they give an archive size of 3.2 MiB.
Assuming a linear relationship, this would be approximately 12.2 Bytes per data point.
Comment: http://ops-school.readthedocs.org/en/latest/monitoring_201.html
(timestamp, value) pairs are stored as a long and a double value consuming 12 bytes per pair.

The 0.2 diff probably due to file  metadata info overhead ?!
Answer: No direct experience with Graphite, but I imagine the same logic as we used for Cacti or anything else RRD or time-rollover driven would apply (Graphite doesn't use RRD internally anymore but the storage logic seems comparable.)
The quick answer is "Probably not as much space as you think you'll need."

The long answer involves some site-specific math.  For our monitoring system (InterMapper) I figure out the retention periods, resolutions, and datapoint size, do some multiplcation, and add in overhead.
As an example I'll use disk space - we store figures with a 5 minute precision for 30 days, a 15 minute precision for a further 60 days, and then an hourly precision for a further 300 days, and we're using a 64-bit (8 byte) integer to store it:

21600 samples total, broken down as:

8640 samples for the 30-day 5 minute precision
5760 samples for the 60 day 15-minute precision
7200 samples for the 300 days 1-hour precision

At 8 bytes per sample that's about 173KB, plus healthy overhead for storage indexing and the like brings it to about 200KB for one partition's disk usage data (any error tending toward overestimation).
From the base metrics I can work out an average "per machine" size (10 disk partitions, swap space, RAM, load average, network transfer, and a few other things) -- works out to about 5MB per machine.
I also add a healthy 10% on top of the final number and round up, so I size things at 6MB per machine.
Then I look at the 1TB of space I have laying around for storing metrics data for charting and say "Yeah, I'm probably not running out of storage in my lifetime unless we grow a whole lot!" :-)
Comment: To throw a number from actual practice out there, with my production retention policies (9 months at 5 minutes ; 1 year at hourly ; 5 years at daily) and about 20 machines with ~20 8-byte metrics each, plus the warning/alarm/critical/outage event histories for 5 years I'm using 1.5G of disk space. That's with InterMapper inserting everything into a Postgres database.  So again - the quick answer is "Probably not as much space as you think you'll need" :-)
Comment: Ya, that math is straightforward, I'm really just looking more on how Graphite stores it data - can make major differences at scale. The only thing I have found is that according to the docs it is not very space efficient (Probably because it counts on fairly aggressive rollups).
Comment: [Whisper (the storage back-end Graphite uses)](https://graphite.readthedocs.org/en/latest/whisper.html) has some built-in space-chewing items -- you've probably already seen that page. The section about "Archives overlap time periods" stands out to me because it means the archives are bigger than my examples above because they all go back to the beginning of time (the 60 day archive is actually 90 days long ; the 300 day archive is 390 days long). Whisper also keeps a timestamp (4 or 8 bytes) along with each data point which needs to be added in too. Doesn't look tricky though, just bloated :)
Answer: I have 70 nodes that generate a lot of data. Using Carbon/Whisper, one node created 91k files alone (the node generates multiple schemas each having multiple counters and variable fields which need to be selectable. eg: (nodename).(schema).(counter).(subcounter).(etc)....and so on).
This provided the granularity I needed to plot any graph I want. After running the script to populate the remaining 69 nodes, I had 1.3Tb of data on disk. And that is only 6hrs worth of data/node. What gets me is the actual flat csv file for 6hrs worth of data is about 230Mb/node. 70 nodes is ~16Gb of data. My storage-schema was 120s:365d.
I'm relatively new to databases, so I might be doing something wrong, but I'm guessing it's all the overhead for each sample.
So it was a fun experiment, but I don't think it makes sense to use whisper for the kind of data I'm storing. MongoDB seems like a better soluton, but I need to figure out how to use it as a backend to Grafana.


Marketing Cloud - duplicate primary key on event data update

Question: I have set up a Data Extension that contains my custom data for Accounts, with a field 'ContactID' that is set as a primary key and mapped to SubscriberKey. I have then created a Journey Builder Event that maps to this DataExtension.
When the Account data changes on the back-end I do a POST /events API call to Marketing Cloud. e.g.
ContactKey='email@example.com', body={"ContactId": "firstname.lastname@example.com", "AccountStatus": "account_pending"}

The first time this works fine, but the second time I post an event on the same Account e.g.
ContactKey='email@example.com', body={"ContactId": "firstname.lastname@example.com", "AccountStatus": "account_ready"}

I get the error:

"The event data contains duplicate value for an existing primary key"

How can I work around this error to get a second event triggered on the same Account?
Answer: The solution we came up with was simply to remove the primary key constraint. This doesnt seem to cause any adverse effects.


Eclipse Search Menus disabled randomly

Question: I use Eclipse 3.3 in my daily work, and have also used Eclipse 3.2 extensively as well.  In both versions, sometimes the Search options (Java Search, File Search, etc) in the menu get disabled, seemingly at random times.  However, with Ctrl+H, I am able to access the search functionality.  Does anyone know why this happens?  Has it been fixed in Eclipse 3.4?
Comment: Have you checked the eclipse bug database?
Comment: I just checked, now that you mentioned it, and didn't find anything...

I'd report it as a bug, but it so inconsistently happens that just saying it happens isn't going to help them track it down and fix it.  I was wondering if anyone else had this problem.
Comment: Same issue for me in Gannymede.  Thanks for the Ctrl+H pro tip.
Comment: It is year 2013. Eclipse Juno is out and is still rampant with this senseless bug.
Comment: There's a lot more bugs in Juno than just that...Doesn't Eclipse have any regression tests?!
Answer: window > close all perspective works for me.
Comment: This did it. Easier than restarting with '-clean'. Thankyou! I hadn't seen this problem in a long time, and it came back today (the bug seemed to be triggered by reopening a very old project, I think).
Comment: - No effect here (kepler). it reverts all perspectives to defaults (darn). Only close/open eclipse works.
Comment: This did it. Thank you! See what I think of Eclipse [here](http://stackoverflow.com/questions/133129/eclipse-search-menus-disabled-randomly#comment36466601_133863). The king is naked!
Comment: on my kepler. it does not work closing all perspective neither closing eclipse works
Answer: Using Eclipse 4.3(!) this happened to me after doing a case-sensitive search.
Window -> Close All Perspectives didn't fix it and neither did restarting Eclipse using -clean. While messing with the search box, I discovered that simply clicking to a previous search entry allowed me to edit it and search again! Clicking back to the case-sensitive search grayed the option out again.
So before you reset anything in your workspace, try pulling up an older search entry using the Down Arrow.
Comment: Only answer that worked for me. This needs more votes, I guess!
Comment: (Answer added because this is the first result for a Google search of "Eclipse search grayed/greyed out")
Answer: I think this answer is what you all need to solve the issue on all versions.
I am using RAD 8 and I have also faced this problem than I removed org.eclipse.search directory in (workspace currently using) workspace/metadata/plugins folder then restart the eclipse.
That's all.
Answer: I don't have an exact answer.  I will recommend that you try to correlate the disablement with which perspective is active.  Likewise, which view is active.  I have been using 3.4 and not experienced this issue.
Comment: Nope - not fixed in 3.4.2 at least.  I've tried changing perspective, refreshing the projects.  It seems to come and go.  Restarting eclipse does fix the issue, or you can do the ctrl-H stuff.
Comment: reproduces with eclipse 3.5 on all perspectives
Comment: Reproduces with eclipse 4.2 on all perspectives. I can't believe the state of computing has become so lousy that a bug like this persists for so long. Fortunately, the workaround suggested by @hgh works, but this is ugly ugly ugly... Microsoft's Visual Studio is so much predictable and professional.
Comment: I have not experienced this issue since I upgraded to Eclipse 3.4.  I guess they fixed it!
Answer: Darn!  I have that problem too -- in Eclipse 3.4.2.
Seems to be related to Navigator and Project Explorer views:
 - Switch to Debug perspective:  Search menu items are there.
 - Switch to Java or Java EE perspective:  Search menu items still there.
 - Click on a project in Navigator or Project Explorer:  Search menu items all DISABLED.
(Curse!  I use search in Selected Resources a lot!  )-:
Hmmm...  It may slso depend on the file type currently open in the editor.  (Like Java vs xml.)
Answer: Still present in Eclipse 3.5.2 -- and for the first time really sticky.
I checked out the "close all opened files and open any other file afterwards" answer and that brought back the Search menu items. Additionally, if you were lucky and have the Search result view open, than indeed there is this little link "Open search dialog".
By the way, additionally lots of other project-related menu items seem to be greyed out also together with this, and they did not reanimate :-( But I did not really check out if these are only items for which it is useful and planned to be greyed out in this situation.
Answer: I'm using RAD 7.5.1 which runs on Eclipse 3.4 and I get this problem frustratingly often. It doesn't matter which perspective or view I'm in, or which editor I have open.
Restarting RAD usually clears it up, but because that's such a colossal pain, I found that you can get around it in the Search View, there is a link; "Start a search from the search dialog" which will bring up the search dialog.
This isn't a great workaround because the link only shows if you have no search history. To do another search, you'll have to clear your search history in the view.
Answer: A late comment for anyone getting bitten by this, but I found "eclipse -clean" fixed it => this does a cleanup of the workspace before starting
Thanks http://letsgetdugg.com/2009/04/19/recovering-a-corrupt-eclipse-workspace/ for the tip, after I guessed my workspace might be corrupt.
Answer: Before search, check you may choose scope in empty Working set. Most Search menu disables Search button when you choose it. And mine, too :)
Answer: window > close all perspectives worked for me too.
But if you are just looking for a text search in the project you could press Ctrl+Alt+G on a marked text
Answer: I have this problem with MyEclipse 7 (eclipse 3.4) under Debian Lenny. Perspective doesn't seem to matter. I get around it with the shortcut Ctrl+H but I was hoping for a better way.
Answer: I couldn't get it to work even when restarting Eclipse.
Here's what worked for me:  Closing all open files and opening a different file.  The different file happened to be .java, but not sure if that had anything to do with it.
Answer: I get this problem from time to time.
In the past I've fixed by starting eclipse with the -clean option.
Once when that didn't work I created a new workspace.
I followed these instructions for those two solutions.
The clean option didn't work for me today and I found this thread because I didn't want to create a new workspace. The closing all files and reopening one file did work however.
Answer: I had this issue also in eclipse 3.6.2: Helios Service Release 1.
Closed all the editor windows, and the search has been enabled.
Answer: Switching to another perspective, then back, works quickly for me.
Answer: I've faced similar issue in Ctrl+H "File Search" tab. The "Search" and "Replace" button was grayed out (disabled). The solution is fill the "File name patterns" text box (for eg, *.py). May be this is by design!
Answer: Just had this problem in Eclipse Neon 3. It is a very common problem in RAD. I could find using  in the console, then switch back to the source and search. RAD would disable the find/search options per source file open. This is very frustrating.
Answer: I had this problem too. It appeared when I installed the m2eclipse plugin.
I had not found a solution, but you can use Ctrl+H shortcut instead.
And you can navigate between tabs with Ctrl+PgDown or Ctrl+PgUp keys.
I've uninstalled the following pluings and it worked.

Maven integration
PMD
eclipse checkstyle plugin
EclEmma (coverage)

I don't know which of those cause the problem. To uninstall a plugin: Help -> Software Updates...-> "Installed Software" tab.

Eclipse Search Menus disabled randomly


Why does $z^n-1=0$ have at max n solutions? $z\in\mathbb{C}$

Question: I know that there is a Theorem which says that a Polynom of Degree n has at most n Solutions, however we have not proved it yet in our class. Is there Maybe another explaination for this Special case?
Comment: induction, starting from a line. next power of polynomial is the previous one multiplied by another monic, degree one polynomial, so QED.
Answer: Because it is a non-constant, single-variable, polynomial with complex coefficients of degree $n$ and the fundamental theorem of algebra says it has $n$ roots in $\mathbb{C}$. Another way to say that is complex numbers is algebraically closed. By a successive factorization argument you can then show that the polynomial has exactly $n$ roots.
Comment: But the FTA is just what the OP has already mentioned, we are looking for a different approach to show that in this particular case $z^n=1$.
Comment: The FTA is about *existence* of roots of polynomials with complex coefficients. The fact that the number of roots cannot exceed the degree is a completely independent algebraic fact.
Answer: By the factor theorem ,  $f(z)$ is divisible by $(z-r)$ for each root $r$.
If there were more than $n$ roots, $r_1,\dots,r_k$, then $f(z)=p_k(z)(z-r_1)\dots(z-r_k)\implies \operatorname{deg}f\ge k\gt n$.
Comment: I think you've got a missing equals sign (I couldn't insert it  for you since I can't save a 1-character edit!)
Comment: You probably mean after $p_k(z)$.  Actually I intended it that way:  I'm trying not to assume anything.   That $f$ is the product of the $(x-r_i)$ might not be clear.  For instance,  I don't want to use FTA.  (Maybe a little silly. )
Comment: Ah, I see. Thanks
Answer: Additions in $\color{blue}{\textrm{blue}}$
$\color{blue}{\textrm{Suppose that}~ z^n-1 = 0~ \textrm{has}~m > n~\textrm{solutions}~ a_1, a_2, \ldots, a_m}$.

Suppose that $a_1$ is a solution of $\require{enclose}\enclose{horizontalstrike}{z^n - 1 =0}$. Then:
$\color{blue}{\textrm{Consider the solution}~a_1~\textrm{. Then:}}$
$$z^n-1 = (z-a_1)p_1(z) = zp_1(z)-a_1p_1(z),$$
where $p_1(z)$ is a polynomial. Since the degree of $zp_1(z)-a_1p_1(z)$ should be equal to $n$, then $p_1(z)$ has degree $n-1$.
Now, suppose that $\require{enclose}\enclose{horizontalstrike}{a_2}$ is another solution. Then:
$\color{blue}{\textrm{Now, consider the solution}~a_2.~\textrm{Then:}}$
$$z^n-1 = (z-a_1)(z-a_2)p_2(z)=(z^2 \ldots)p_2(z).$$
This time, $p_2(z)$ should have degree $n-2$.
In general, given $k$ solutions $a_1, a_2, \ldots, a_k$, we ca write:
$$z^n-1 = p_k(z)\prod_{i=1}^{k}(z-a_k),$$
where the degree of $p_k(z)$ is $n-k$. Of course, this can be reiterated up to $p_n(z)$, which has degree $n-n = 0$, i.e. it is $p_n(z) = p,$ a constant. Formally:
$$z^n - 1 = p\prod_{i=1}^{n}(z-a_n).$$
Then, you have $n$ solutions $a_1, a_2, \ldots, a_n$. Of course, if some $a_i$ coincide, then you have at most $n$ solutions.
$\color{blue}{\textrm{In conclusion, the number of solutions cannot be}~m>n, \textrm{but}~ m\leq n}$.
Comment: @gimusi they don't assume that a polynomial of degree $n$ has at most $n$ roots. They proof it for this particular one. Granted the argument they use for the special case essentially shows the full result in that sense this answer is not a different explanation. However it seems more plausible to me than a misunderstanding  that OP wanted an argument that does not presuppose that result, and just that rather then an substantially different argument. (What they may not have realized is  how easy the proof of that result is.)
Comment: @the_candyman No in my opinion you don't need to remove that, it's up to the asker evaluate things, revise its work and then ask for clarifications if needed. You could revise it a littele bit giving some clarification of course but also that it's up to you. Bye
Comment: @the_candyman What is really sad for the reliability of the site is that some answers (maybe wrong or maybe correct) have been downvoted but other answers (I suppose not adressing the OP) have been upvoted or not downvoted. The only explanation I can find is  a targeted downvoting and I can also accept that. But in any case we should work in such way that a good answer remains here for the asker and for futur users.
Comment: @the_candyman Now it seems fine to me.
Comment: @the_candyman I'm here mostly to learn and I'm always happy when we can discuss honestly about our thoughts and effort! Thanks for your efforto to improve your answer. Bye
Comment: It seems yor are assuming the thesis as hypotesis or am I wrong?
Comment: Without using the fundamental theorem of algebra is there any way to say about the existence of root?
Comment: @gimusi and (at)Shubnam For sure, this answer does not substitute the f.t. of algebra. Given that solutions exist, I showed that the polynomial can be factorized. Since this process can be performed $n$ times, this means that the original set of solutions must not exceed $n$.
Comment: That's the reason why I think that your is not an answer to the OP and maybe the asker has not understood the meaning of what you have done.
Comment: @quid Thanks for your comment and observation. Regards
Comment: @gimusi and (at) quid. I totally agree with you. If my answer can be misunderstood by OP, then I'm going to remove it. What do you think about this option?
Comment: @gimusi I've edit my answer a little bit. Hope you can check it and send me your feedback.
Comment: @gimusi thanks for you invaluable support :D
Answer: There's an explanation if you represent them in polar co-ordinates and consider that multiplying two complex numbers involves adding their arguments (ie angles) and multiplying their magnitudes (distances from the origin). It turns out they need to have $1$ as their magnitude and be multiples of$\frac{360°}{n}$ apart on the resulting circle, so only $n$ of them will fit.
(This is effectively the same as gimusi's answer.)
Edit: In fact, there are exactly $n$ of them, and they're equally spaced round the circle. The reason should be obvious if you pick one of the candidate angles and multiply it by $n$.
Comment: Thanks. I don't feel I understand a piece of maths until I can explain it in words, so I'm trying to do that! I think the symbols are just a means of manipulating the cincepts, and I'm trying to get better at understanding the conceots.
Answer: First fact: for complex (nonzero) polynomials $f(z)$ and $g(z)$, the degree formula holds:
$$
\deg(f(z)g(z))=\deg f(z)+\deg g(z)
$$
where $\deg$ denotes the standard polynomial degree.
Proof. If we write
$$
f(z)=az^m+f_0(z),\qquad g(z)=bz^n+g_0(z)
$$
where $f_0$ and $g_0$ group together the lower degree terms, $a\ne0$ and $b\ne0$, then
$$
f(z)g(z)=abz^{m+n}+h(z)
$$
where again $h(z)$ has degree less than $m+n$. Thus $f(z)g(z)$ has degree $m+n$. QED
Second fact (basic and well known: if $a$ is a root of the polynomial $f(z)$, then $f(z)$ is divisible by $z-a$.
Now we prove by induction on the degree of $f(z)$ the following statement.

Let $f(z)$ be a nonzero polynomial with coefficients in $\mathbb{C}$. Then the number of distinct roots of $f$ cannot exceed the degree of $f$.

The statement is obvious for polynomials of degree $1$. Assume we know it for polynomials of degree $n-1$. Let $f(z)$ have degree $n$ and let $a_1,a_2,\dots,a_m$ be its pairwise distinct roots. By the second fact, we have $f(z)=(z-a_m)g(z)$ and $g(z)$ has degree $n-1$. Now, for $k=1,\dots,m-1$,
$$
f(a_k)=(a_k-a_m)g(a_k)=0
$$
and, since $a_k-a_m\ne0$, we conclude $g(a_k)=0$. Therefore $a_1,\dots,a_{m-1}$ are pairwise distinct roots of $g(z)$. By the induction hypothesis, we have
$$
m-1\le n-1
$$
and therefore $m\le n$. QED
Note. This proof applies with no change to polynomials having coefficients in an arbitrary domain.
Answer: We have that
$$z^n=1\iff z^n=e^{i2k\pi}$$
and then
$$z_k=e^{i\frac{2k\pi}n} \quad k=0,\ldots,n-1$$
and those are the $n$ roots of unity.
It is trivial to see that the solution is periodic since $e^{i2kπ/n}$ for $k=k_0$ and $k=k_0+n$ represents the same complex number.
Refer also to roots of unity for details.
Comment: This doesn't really explain anything at all. You've shown $n$ solutions, but there's zero reasoning about why there aren't $n + 1$ solutions. In other words, your $\iff$ basically is just a rephrasing of what the asker already knows.
Comment: So for the briefest possible explanation of my issue with this answer: The question asks why there are **at most** $n$ roots of unity. You've (not quite, but almost) shown that there are **at least** $n$ roots of unity.
Comment: I certainly agree that it's easy to see that $e^{2\pi i k / n}$ satisfy $z^n - 1 = 0$, but I stand by my statement that you haven't shown that these are the *only* roots of unity.  In other words: you have not included any explanation for why a polynomial of degree $n$ has at most $n$ roots. So you've only got half a solution, compared to the other four answers that *do* address this issue.
Comment: @T.Bongers I'm  assuming that the asker already knows the topic and in particular the complex roots of unity. Once we have given a suggestion for that he/she is able to conclude by him/herself the doubt "Is there Maybe another explaination for this Special case?". Anyway now I've also add what I've already pointed out in the comments.
Comment: My informal "only $n$ of them will fit" and gimusi's remark about the solution being periodic are saying the same thing. But neither of us has quite said explicitly that a repeated root only counts as one root (ie that we're not using the trick of turning the complex plane into a Riemann surface, if I've remembered its name right.)
Comment: I think that the problem that people have with this answer comes down to the fragment "and then (...) and those are the $n$ roots of unity". Your argument of "periodicity" only shows that, **among the numbers of type** $e^{i2k\pi/n}$, there is only $n$ different ones. It doesn't shed light on why there couldn't be a different kind of solution. (For example, some $2e^{1+3i}$ or something like that.) You just state, without further explanation, that the only type of solution is of that form.
Comment: @AloizioMacedo Thanks a lot, I'll reconsider my work and I'll take into great consideration you kind observation. Thanks for your time! Bye


Is it safe to give candies to my parrot?

Question: Can I give candies to my gray parrot? He like candies and cookies.
Answer: In general, many animals, including parrots, should not be given foods very high in sugar, fat, or sodium. It is not technically toxic, but too much of these things can cause various medical issues. There are also a variety of foods that are toxic or possibly toxic to parrots that can be found in sweets:

chocolate
licorice
xylitol - a sugar substitute that can be found in sugar free candies
peanuts
dairy (not toxic, but parrots are definitely lactose intolerant)

There are also other foods that are toxic that are less likely to be found in sweets. The following is not necessarily a comprehensive list of all things that are poisonous to parrots.

Avocado
Mushrooms (generally of the varieties not safe for human consumption either)
Fruit seeds and pits such as apple seeds
Plants from the allium family (garlic, onions, and so forth)
Plants from the nightshade family (not including the fruit, as in tomatoes are okay)
Comfrey, the herb
Leaves from the rhubarb plant
Answer: "Safe" is an illusion. The "safest" thing to do is to not being born.
I know parrots who eat a little bit of chocolate now and then. They are still alive.
Xylitol is not "artificial", it is birch sugar. Some people seem to compare it to aspartame (which is complete and utter nonsense).
Some people also seem to think that the bacteria in our saliva are poisonous to parrots. My own experience proves that this is NOT the case.
Then there is this narrative about parrots being lactose intolerant. That too, according to my own experience, is nonsense. Our parrots eat yogurt every day and after many years, they still live happily without ever having diarrhea.
Comment: Welcome to pets.SE! It is not common here to criticize another answer via a second answer. For helpful critics, like hints how to do better or questions for clarification, the comments are used (and firsthand the voting!). And yes, you could not use comments until now, because a basic amount of point is needed, which secures, that the user have some experience before the first comment. Your option to "critical doubt" the other answer is to write an own answer to the question, which directs the questioner. The question in this case is very short and do not includes "safe" or "lactose" in it ;)
Comment: I always assume people calling xylitol "artificial" just use this word as a misnomer for "sugar substitute". And xylitol's natural origin doesn't deny the fact that it is actually toxic to dogs and cats - I'm not familiar with its effects on birds, though. Also, lactose is digested by bacteria during lactic fermentation in which yogurt is made, it gets converted to lactic acid; yogurt, like all fermented milk products, doesn't contain significant amounts of lactose.


Intellij IDEA Community Edition - commercial proprietary software developing

Question: Can I use free Intellij IDEA Community Edition for the developing, if I'm working on the proprietary commercial product?
Answer: Yes.
Intellij IDEA Community Edition is (almost) entirely licensed under the Apache 2.0 license (http://www.jetbrains.org/display/IJOS/License+Information).
The Apache 2.0 license allows for commercial use (http://choosealicense.com/licenses/apache-2.0/).

This is not legal advice.
Comment: The license covers both using the IDE and developing a derivative of the IDE. See http://www.apache.org/foundation/license-faq.html#WhatDoesItMEAN "It allows you to: freely download and use Apache software, in whole or in part, for personal, company internal, or commercial purposes;". By "in a commercial fashion" I mean something like "your use of the IDE can cause you to gain money". I understand the question the same as you - but the licenses cover both use of IDE to create software and its modification. And the use of IDE to produce commercial software is permitted by all JetBrains licenses
Comment: Does the license really matter here? So I can't develop a proprietary software product if I'm using the proprietary Intellij IDEA Ultimate?
Comment: The license matters. Community Edition is licensed under the Apache license which allows you to use the software (the IDE) in a commercial fashion. IDEA Ultimate is licensed under JetBrains' proprietary license which explicitly allows you to use it in a commercial fashion.
Comment: so both allow you to use them in a commercial fashion? Probably it's a typo in your comment. And what do you mean by "in a commercial fashion"? Let me rephrase my question. Let's say I'm developing a shopping web site. Is there a difference in what edition of Intellij IDEA I use as to what license I have to apply to the code of my web site? My understanding is that the top question is not about developing an IDE based on the Intellij IDEA, but about developing a normal software product.
Answer: The following is my understanding of the problem:
You are not restricted to what kind of software you develop unless you are developing a product that is derived from Intellij IDEA, for example, if you are developing your own IDE that is derived from IDEA.
That being said, you can even use the commercial version of Intellij IDEA to develop a commercial product that is not an IDE itseft and doesn't use Intellij IDEA's source code.

This is not legal advice.
Comment: Are you able to provide a citation for this?
Comment: @PatW. No, I can't. I'm not an expert here, that's why I said that it's my "understanding". I do believe it would be absurd otherwise. I think the question comes from the misunderstanding of the difference: "using a tool" vs "deriving a product from a tool".
Comment: From https://www.jetbrains.com/idea/features/editions_comparison_matrix.html if you hover your mouse over the "i" for the license information of the community edition it says: Community Edition is open-source, licensed under Apache 2.0. Projects like Android and Swift use Apache 2.0, so you're in good company. It can also be used for commercial development.
Answer: In addition to the Apache 2.0 license for IDE, there are also now some bundled with plugins that are now proprietary JetBrains license: https://www.jetbrains.com/legal/community-bundled-plugins/?product=iic&version=2021.1.
There doesn't look to be any restriction on using those plugins for a commercial purpose.


How do I convert this excel formula to work in Google Sheets?

Question: In excel I have this:
=INDEX(PayoutID,MATCH(TRUE,COUNTIFS(INDIRECT("'"&PayoutID&"'!$D:$D"),$A3)>0,0)) in B3
It looks at cell A3, then using a named range PayoutID (a list of sheet names), it finds the number in A3 and reports the sheet name.  All good.
When I import in to google sheets it converts it to this formula:
=ARRAY_CONSTRAIN(ARRAYFORMULA(INDEX(PayoutID,MATCH(TRUE,COUNTIFS(INDIRECT("'"&PayoutID&"'!$D:$D"),$A6)>0,0))), 1, 1)
This only works if the match is made on the first sheet name listed in the named range. Once it's done that one it shows #N/A for the rest.
Can someone amend my Google Sheet formula so it will work across all sheet names in the named range regardless of if there is 5 or 50??
I've spent a lot of hours searching and trying different things and cannot get it working.
Ultimately it is not finding a match, but that is only because it's not looking in all sheets listed in the named range.
Answer: Try:
=ARRAYFORMULA(XLOOKUP(1,N(BYROW(PayoutID,LAMBDA(ζ,COUNTIF(INDIRECT("'"&ζ&"'!D:D"),A3)))>0),PayoutID))


Used ceiling fan not working

Question: Bought a used ceiling fan w 2 pull chains and lights. Seller assures me it was working. Hung it up and wired it fan black and blue to ceiling black, white to white, and both a  green wire from the down rod and a green wire from the fan hanging ball to the ceiling copper wire. Multimeter test shows 120v when red probe is touched to light socket and black probe to housing screw head. Pull chain to light shows 0 when chain is pulled off. Was a ceiling light with a single wall switch. Why is neither the lights or fan coming on?
Comment: The seller assured you the fan worked. Are you 100% he wasn't stretching the truth?
Answer: You are testing hot (light socket center) to ground (housing screw) and getting 120 volts. How about between light socket center and light socket screw threads? This will test hot to neutral which is where you need the voltage. Assuming this is not near 120 volts, it sounds like your neutral (white) wire is not connected. You should probably take down the fan and test voltage between black and white wires or, better yet, reconnect the old light to test. Assuming this works, reconnect the fan, making sure the get good connections with the wirenuts.
Comment: Ceiling black to white shows 0 on the multimeter. Previous light fixture worked. What happened?
Comment: @SField Do you know how the original light was wired? It's possible that the neutral/white wire in the ceiling is broken and someone used ground in place of neutral. This will work (provided the breaker is not GFCI) but is not legal and is potentially very dangerous! Otherwise, check the ceiling to see if there was a wirenut connecting the white wire to another; it may have come loose. Somehow, the neural is no longer working.

Used ceiling fan not working


The difference between two phrases

Question: I need to know the difference between two phrases "learn by heart" and "learn by rote". I would be grateful if you could explain it to me. I'm not a native English speaker.
Answer: Welcome to EL&U. The difference is this: "Learn by heart" refers to the level of learning while "Learn by rote" refers to the method of learning. For instance when it comes to he arithmetical 'times tables' (2 times 2 is 4, 3 times 2 is 6 and so on) most children learn them by heart so that they can repeat them and, perhaps more importantly, can recall individual items randomly and in reverse so that they can do simple division in their heads (for instance 'how many times does 7 go into 42?' answer '6').
The method by which most children learn their tables is by frequent repitition of the tables. This is 'learning by rote'.
Answer: To learn by rote is to effectively memorize a series of steps and conditions, with the objective of accomplishing a goal. This method has drawbacks if sufficient consideration for complications are not taken, especially if the learner is unable to memorize all the possible conditions which may arise.
To learn by heart is similar in concept, but without the constraints of a specific sequence. One can learn by heart (memorize) a specific series of steps but not have the limitations of only executing them in the memorized order.
The former typically does not require an understanding of the tasks to be performed.
To learn by rote could be considered a subset of "to learn by heart."

The difference between two phrases


Theoretical power limit of nuclear bomb

Question: Is there any limits of power or power to mass (or any other) limits for nuclear bombs?
I found this wiki article: Nuclear weapon yield: Yield limits. Is the information provided is correct? If yes, from where this limits come from?
Answer: The sun and all other stars are in effect thermonuclear bombs. If they get heavier than about 10 times the mas of the sun they eventually blow up as a supernova, so there is a limit to the size but it's a lot larger than anything we will ever build.
In the wikipedia article, the yield limits have to do with deliverability. It's no good having a huge bomb if you can only explode it in the factory where it's made. They're talking about "6 megatons per metric ton" so a 60 megaton bomb would weigh 10 tons. The article gives examples of delivery, with the limit being a 1.3Gt bomb deliverable by an Antonov An-225.
Answer: Nobody really knows.
The Tsar Bomba was a 50 megaton explosion, weighing 27,000 kg
https://en.wikipedia.org/wiki/Tsar_Bomba
It was scaled down from a 100 megaton design to reduce the fallout created.
The blast did damage up to 900 km away, and despite detonating 4200m above surface, caused seismic disturbance greater than 5 on the Richter scale.
No one has dared test a larger design -- but much like huge draglines and dumptrucks, no one WANTS to push the design to the upper limits.  You can get better results, more reliability, and greater fault tolerance delivering more, smaller bombs.
The Tsar Bomba actually sent most of its energy into space, and not along the surface -- which is what you want a bomb to do -- so BIGGER yield may not in fact scale to bigger damage.
Speculating about thermonuclear weapons is really all we can do
https://en.wikipedia.org/wiki/Thermonuclear_weapon
because real knowledge remains closely controlled.
The Tsar Bomba was speculated to have had multiple tertiary stages.  It is unknown how many teritary stages can be chained together. The bomb basically explodes in a spherical fashion.  As the radius of the sphere increases, the volume involved cubes.  To work, the stage must compress the layer above it to fusion temperature and density and hold it there long enough to create yield.
No one knows the upper engineering limit of success -- because no one has tried and failed to exceed it.  It is much like the question "how large an aircraft can be constructed and flown."  Unknown.

Theoretical power limit of nuclear bomb


Does victory point determine resource base opponents in Boom Beach?

Question: Does current victory points of the player determine the opponent player one is matched against?
Answer: According to the Boom Beach Wikia, the game does not care if the opponent has a high or low level at all. It only cares about the amount of Victory Points you have. The more Victory Points, the higher the level of the average opponent will be. This will also affect the resources bases you receive (occupied by opponents of course) as the owner of the base must have just enough Victory Points to become your opponent.
Yes, I've seen level 20's when I was a level 35. Do not underestimate the attacking power of weaker opponents, they can surprise you on how good they can be. Unclaimed resource bases' levels will go higher as you unlock more and more segments of the Archipelago, regardless of your current level or VP count.

As your Victory Point count goes up, you will be matched up against harder Blackguard bases and player bases with similar Victory Point counts. Typically, higher Victory Point counts mean you will be matched up against higher level players. Your Victory Point count DOES affect what players own the Resource Base that you discover or refresh, but please note that Victory Points DO NOT affect the difficulty of Lt. Hammerman bases, Colonel Gearheart's War Factories, and Dr. Terror levels.
Answer: Yes it is based on your current victory points, read here on the Boom Beach wikia Sorry I can't be in more depth with this answer, it looks like you are looking for a simple Yes or No, if you want further information, edit it into your question and I'll go digging around and then edit my answer.
Comment: I have seen the page you mentioned but i don't quite agree to it. I have user bases of level 35 on my map though the resource bases i have on my map are as high as level 50.
Answer: Sure it is !
The level doesn't change anything, only Victory Points. I'm level 46, with 580 VP, and my opponents are level 50-55 etc...
It depends of your place in the leaderboard ;)


How to backup and restore to different hardware in Linux?

Question: I am running Fedora 22 on a Dell Laptop. I plan on migrating to a desktop soon which will also run Fedora 22. What is the best way to go about backing up and restoring my laptop configuration to the new system? I do not have any 3rd party backup/restore software on this system. Would dd be able to work for me? Would a system level backup work or would I need to limit dd to partitions that are not "hardware or device" specific. I am also open to any other suggestions or ideas.
Answer: I second the approach of doing a fresh install and then rsyncing /home. But, for completeness, if you want to move your disk from one computer to another with another hardware — either literally or by using dd to copy the contents, make sure you run
sudo dracut --force --no-hostonly

on the machine before you make the backup or copy.
This will generate a generic initial boot image.
By default, Fedora saves space and time by creating boot images which may be specific to your particular hardware.
If you forget to do this and the machine won't boot (due to missing hardware support in the boot image), use the Rescue Mode menu entry at the initial bootloader screen — this always has a larger, generic boot image, and will get you into the system and from there, you can run the dracut command to generate an initial ramfs for your non-rescue environment. (In that case, though, you'll have to identify the kernel version. Look in /boot, and provide the number, like this: dracut --force --no-hostonly --kver 4.2.3-300.fc23.)
Comment: Can you elaborate on that instruction? Perhaps provide a step by step? I.e, when do I run that command? At what point in the process and on which machine?
Comment: There's just the one step. :) But, yes, run it on the machine that you're backing up before you do it.
Answer: There are several different options here, each with different effects and tradeoffs.
Firstly, you probably don't want to do anything with dd. dd runs a block-level copy; it mirrors a disk image precisely, without caring about files. This will carry files in their associated filesystem along, but there are problems here: if both devices are in the same machine, you may have confusion due to identical UUIDs; it obviously precludes any filesystem-level changes you may wish to make, such as migrating between filesystems, allocating more inodes, or whatever; and it requires that the destination block device be the same size as the source, which is often not the case. (If the destination is larger than the source, it'll still work, but you won't be able to access the extra space until you run a separate resize operation. If the destination is smaller, it'll fail and you won't be able to access your data, even if there was enough free space in the filesystem.)
The main use case for dd is probably if you're cloning root or boot filesystems from one machine to another, which is a somewhat fraught topic on its own. Here dd is appropriate because you usually want to preserve FS UUIDs and so forth, in order to keep the boot process working. But you probably don't want to do this. (The other use is literally dealing with disk images of USB sticks, CDs and so on, but that's not as relevant here.)
What you more likely want to do is a file-level backup/restore. For this I've found rsync to be excellent, if both machines are up at once; if not, it may be better to use tar. Assuming you've run a fresh Fedora install on the desktop system, you should be able to rsync/tar migrate the /home directory from one machine to the other. This will preserve all user files and most user-level customizations (the exceptions being things like crontabs which are stored outside /home). Then, in order to mimic the old setup properly, what remains is just to install all the same software through the package manager. Due to keeping the home directories, where most software stores its configuration, installing it again should leave you with things working the way they were.
Comment: Great information on dd. I'll look into rsync. Thanks Tom.
Comment: Sounds like he wants to clone his laptop drive to another machine, which sounds like a good use case for dd. Use a live system and a network share or external drive for the backup, run `dd if=/dev/sda of=drive.dd.img` on the laptop and `dd if=drive.dd.img of=/dev/sda` on the new computer. Be careful - if you misspell if/of, it will *not* ask you before overwriting the wrong drive!
Comment: @basic6- Yes, that is what I want to do. If I followed your instructions, would I need run the dd restore command on the new systems while booted from a liveCD or is there another way? Are you sure dd would work in this scenario?
Comment: The problem with cloning the whole drive is 1. you need to adjust the size afterward, or else you can't use the extra space (even more of a pain with partitions), 2. you can't be sure hardware is compatible (don't know about Fedora, but a lot of distros do some machine-specific stuff at install time). The problems this can cause are subtle enough that I'd generally recommend a fresh install and file-level copy instead.


Where are My.Settings saved in VB 2010 .NET?

Question: Are My.Settings values saved in the program itself or do they get stored in the registry? So, for example, if I set a My.Settings value with a program, then I copy the program itself to another PC - is the My.Settings value still set?
Comment: no, if it is User settings. Only Application Settings would come to your application.
Answer: It depends upon the scope you have selected. There are two scope settings - Application and User scope.
From MSDN article:

Application-scoped settings are read-only and are shared between all
  users of that application. These settings are stored in the app.config
  file in the  section. At run time, the app.config
  file will be in your bin folder and will be named with your
  application's name (MySettingsDemo.exe.config).
User-scope settings are specific for each user. They can be read and
  set safely by the application code at run time. These settings are
  stored in a user.config file. To be technically accurate, there are
  two user.configs per user per application—one for non-roaming and one
  for roaming. Although the Visual Basic 2005 documentation states that
  the user.config file will be named according to the user's name
  (joe.config), this is not the case. The user.config file is created in
  the:

<c:\Documents and Settings>\<username>\[LocalSettings\]ApplicationData\<companyname>\<appdomainname>_<eid>_<hash>\<verison>.

Answer: Dim config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal)
MessageBox.Show(config.FilePath)

Comment: This is the only correct answer, that is independent of VS version. For per-user installs they are stored in something meaningless like C:\Users\\[YOURNAME]\AppData\Local\Microsoft_Corporation\DefaultDomain_Path_jojpsvsna1vaszvd35jsryd0vnvv001i\16.0.11601.20144\user.config
Answer: If you have installed your application using clickonce then your MySettings will be stored in a config file which is stored at `C:\Users\\AppData\Local\Apps\2.0\Data........
search in these path with a file named as yourapp.exe.config
The thing is MySettings will be stored in app.config file of that application and after publishing the app.config file is saved as applicationname.exe.config file
Answer: They're definitely not stored within the program if they're User settings - that's not very easy to implement, and rather pointless. Rather, they're stored in a configuration file in the %AppData% folder. So no, if you copied the program, the User settings wouldn't come with it, just the Application settings.


Samsung MZ-76E250B/EU 860 EVO for raspberry pi 4?

Question: I just bought my first raspberry pi and would love to attach an SSD. In search of good value for money, I came across this drive from Samsung. Does someone already have experience with it? I am particularly unsure about the power supply.
Comment: Of all HDDs / SSDs I own, I haven's seen a single one which wouldn't work with a Pi.
Comment: I have been using a couple of SamSung T5 500G/1T SSDs for about one year.  So far so good, and I am loving it: https://raspberrypi.stackexchange.com/questions/100353/can-the-3b-power-two-usb-ssd-drives. Cheers.
Comment: PS - My SSDs are USB but yours is SATA. I remember I once used SATA SSD for my evil WinPC and found it good. But I don't know how to connect a SATA SSD to Rpi, it might be hard to do so. :( Anyway, good luck and cheers.
Answer: Yes, a 860 EVO 500GB works for me at least on Raspbian buster, Pi 4 with this USB 3.0 to SATA adapter  https://www.amazon.co.uk/ELUTENG-External-Support-Adapter-Compatible-Black/dp/B06XCV1W97/&qid=1587037480&sr=8-2.  No additional power needed, I'm using the official universal micro USB power supply.


Best free PDF generation library for complex layouts

Question: Which is the best free library (for whatewer programming language) for generating PDF with complex layouts (many pictures, text in arbitrary positions etc)? It should be best suited for drawing, not report generation. I'm considering prawn, but not shure if there exist a better solution. Any suggestions?
Answer: You may want to try Haru Free PDF . Also see this Wiki article


Can any piece of knowledge be produced without depending on another piece of knowledge?

Question: In the case of sciences, for example, can the birth of a new branch of science be considered as utterly "new"?
Comment: One liner questions are typically too vague to permit reasonable answers, please provide more context and specifics of your thoughts on the subject, such as what "utterly new" and "depending on another piece of knowledge" mean. There is a sense in which everything depends on everything else so without better specification this is unanswerable or trivial.
Comment: does this include prior information?
Answer: It depends on what you mean by 'can'. Logically, I suppose this is possible. There is no contradiction in saying 'X is a new branch of science and it is utterly new', i.e. without precedent or prefiguration in existing or previously existing science.
Historically and empirically, there are few or no absolute beginnings in science. One science emerges from another. I think this happens in two broadly different ways.
▻ Revolutions in a field of inquiry create new conceptual schemes
Think of physics. There is the physics of Aristotle, then the physics of Ptolemy, then the physics of Copernicus, then the physics of Newton, then of Einstein, then of quantum theory, now of string theory. In each case a conceptual revolution occurred that created in all but name a new science. And each revolution happened because of perceived defects in previous theories.
▻ Progressive refinement
What starts out as a gross, undifferentiated subject matter breaks down into sub-inquiries : in physics, for example, astronomy, dynamics, mechanics, optics,  and any number of other fields progressively emerged. New fields of inquiry separated themselves as distinct groups of problems were recognised. But they all developed from existing inquiries.
▻ New combinations
Plainly the intersectional or bridge disciplines such as bio-chemistry, bio-physics, &c. could only emerge from pre-existing sciences.
Comment: @Selin Köksal. You have an answer to your question.
Comment: Users are automatically notified when a new answer is posted to their question, there is no need for addressed comments.
Comment: @Conifold. : versato in rebus cedo.


Create tracks from GPS points honoring polygon barriers

Question: I have fish tracking data from a river. The data include positions, times and tag ids. Time interval between positions may be several days.  I would like to create a polyline track for each fish tag that stays within a polygon that defines the shoreline of the river.  I am looking for a procedure or extension or add-in to use in ArcGIS or one of several open source GIS.
Comment: I hesitate to suggest this because it could be extremely time consuming, but theoretically you could use your river feature class as a cost surface and calculate the least cost path between each location and the next location. This would force the lines to stay within the river banks.
Comment: @phloem I've just done this using R - the time consumption will be dependent on the resolution of the rasterized river map and the number of points to be interpolated. But my example below runs pretty quickly on my 6 year old laptop.
Answer: Here's a solution using the gdistance package in R for computing shortest paths according to a cost surface derived from a raster:
First read in the raster of the river map. In my case this has values of 0 for the rivers and 255 for dry land:
> require(raster); require(gdistance)
> rivers = raster("./surface.tif")

Next convert to categorical data, with a cutoff anywhere between 0 and 255 - this defines which values are river and which land:
> rfac = asFactor(rivers<100)

Now compute the transition matrix based on this categorical raster, using the values to define areas where paths can go, and an 8-direction transition. Bump this to 16 if you want finer detailed paths (but takes longer to compute):
> rfactr = transition(rfac, "areas", 8)

Now I have a little matrix with the first row the start and second row the destination:
> pts
          [,1]     [,2]
[1,] -10268153 16602667
[2,]  -9064803 15332707

Now compute the shortest path and return a lines object (can also return a raster cell coverage raster):
> path = shortestPath(rfactr[[1]], pts[1,], pts[2,],"SpatialLines")

And lets see the magic:
> plot(rivers)
> lines(path,col=2,lwd=2)
> points(pts)

You only need compute the transition matrix once, computing more paths is just a call to shortestPath, which took about a second on my very old laptop. It'll depend on the resolution of your raster, in my case this is 555x783 pixels. A modern machine could do this in the blink of an eye. Must upgrade...
If you've not used R before then be assured its pretty capable as a GIS with a programming language attached...
Answer: Both ArcGIS and QGIS would do the trick (assume you have got a csv spreadsheet in hand):
ArcGIS version:

Use 'Add data' to add load your csv file onto ArcMAP;
Right click the csv table choose 'Display XY', and set the right position field.
Right click the new .event layer, export it to a shapefile (now you will have a point layer you can work with).
if you have the polygon in hand already, you can then use 'Clip (Analysis)' tool to get all fish tags within that polygon (choose your polygon as then clip feature).
lastly use'Points To Line (Data Management)'to create a line track.

QGIS version:
Simlar to ArcGIS: whereas in QGIS you will use 'Create a Layer from Delimited Text File' tool to load csv data, and Clip under 'Vector -> geoprocessing toolset'. I suggest you check out this plugin here: http://spatialgalaxy.net/2011/12/30/qgis-plugin-of-the-week-points-to-paths/
Comment: I think they were looking for a way to constrain the line within the river banks, which this will not do.
Comment: Phloem is right.  all our fish locations are within the river, but connecting points to create a track generates tracks that cross land where the river goes around a bend or a peninsula sticks out into the river.  I am looking for a way to keep the track in the river.


Penny-farthings: Skills required to transition from standard bicycles?

Question: Beyond the obvious difference of the saddle being 5 feet high, how is riding a penny-farthing different to riding a standard road bike? What unique skills are required to ride a penny-farthing?
Comment: Also related, Mike Boyd made a YouTube vid of himself learning to ride a penny farthing. https://youtu.be/QpAkhMmD3WA
Comment: GCN have a youtube video on penny-farthing riding. It gives a good insight if you haven't yet watched it.
Comment: This might be a good opportunity to use safety equipment.
Comment: @DavidD If you go to the link in the "Conclusion" section of the Answer- http://www.penny-farthing.org - you'll see I do some extensive coverage of protective equipment I've found useful
Comment: Not a duplicate but relevant: https://bicycles.stackexchange.com/questions/55054/how-to-start-riding-a-recumbent-bike
Answer: Intro:
Road cyclists often ask me this question when they encounter me riding my penny-farthing. It's a mystical beast little understood by many cyclists, so I'll take a moment to demystify the PF and the skills required to transition from riding a road bike to a PF.
There's actually a lot of overlap between the skills keen road cyclists rely on to stay alive sharing the roads with motor vehicles in respect to defensive cycling and also the Highway Code's strictures on cycling. Signalling and lane usage in respect to turning is exactly the same.
But the key skills unique to riding a penny-farthing that a road cyclist must learn can be summarized as:
Mounting & Dismounting:
Unlike a standard road cycle, mounting & dismounting is a 2-step process and must be mastered to the point that you can accomplish it without even thinking about it before venturing out onto the public roads. The PF cyclist has the intermediate task of stepping onto the mount pegs both before mounting & dismounting. However, with a little practice, it's really not that difficult as it sounds and can be learned in probably 1-2 hours of consistently practicing the skill. You'll see next that this is even a foundation skill to moderating speed... I've put together a fairly comprehensive video of the mounting/dismounting process which also discusses how to avoid it all going wrong, or if it does, minimising injury on bad mounts/dismounts.
Speed Moderation:
There's no gearing on a penny-farthing, so if the cyclist wants to go faster, they pedal faster; no different than a conventional road bike. But, it's not increasing speed that's the challenge for a PF cyclist, but rather decreasing their speed. This is accomplished either using resistance on the pedals or a mechanical brake - usually a caliper type on modern PF's - on the small rear wheel. However, unlike a standard road cycle, a PF cyclist should not mash down the rear brake while on the saddle- it will cause the back wheel to judder and become unstable. Ideally a mechanical brake is most safely- and effectively- applied while standing on the mount pegs as this forces weight over the small wheel.
And more importantly, applying a mechanical brake- assuming one is fitted- from your mount pegs provides the cyclist the option to either remount or dismount depending on the reason they needed to brake. When I began cycling Penny-Farthings, I learned with leg-braking only which also ensured I never cycled faster than I could brake with negative resistance on the peddles.
Changing Direction:
On a standard road bike one can make relatively sharp turns; don't ever try this on a penny-farthing. Turns must be gentle and wide on a PF or the rider can be sent over the handlebars if the turn is too sharp.
But it's in respect to changing direction in relation to traffic that is the challenge for the penny-farthing cyclist.
Like road cyclists, PF riders have to slow when approaching a junction or roundabout to assess whether it's safe to proceed into it. However, unlike road cyclists, PF riders have the intermediate step of both moderating their speed and halting from their mount pegs; both are a two-step process. They must be prepared to either speed up and enter the juncture/roundabout, or step down and halt if it's unsafe to proceed. So changing direction is a bit more complicated than on a standard road cycle.
Headovers:
Small road debris and potholes that a road cyclist might be able to pass over safely could cause a Penny-Farthing rider to go over their handlebars - a "headover" causing serious injury or death. The rider's weight is directly over the large wheel which makes a PF quite twitchy. Anything that impedes the large wheel even momentarily could send the rider over the handle bars. One must always cycle over flat, even surfaces and navigate around ALL debris & potholes. Don't ever go through a deep puddle if it could conceal a branch or pothole.
Managing Risk:
When approaching tricky situations like busy roundabouts, do so on your mount pegs where possible. Obviously is the approach is uphill this isn't possible. But by being "Half-On, Half-Off" you're in a good position to halt if the roundabout/juncture is too busy to join safely, and if it isn't, you just re-mount the saddle and continue peddling. But as you can see, being able to quickly find your mount pegs to get in the "Half-On, Half-Off" position is essential.
Training:
You should gain these essential skills on roads where there is relatively light traffic and good visibility for you to see motorists and they to see you to enable you sufficient lead time to stop if necessary. With time & miles this will become second nature, but when you're learning, you'll need that extra time to dismount. You are asking for trouble if you venture out onto busy London roads while you're beginning. I learned the basic skills in my own housing development which has a main road with a few roundabouts in it. And I'd practice outside of busy periods like morning and evening rush hour traffic. I don't care how confident you might feel, it takes time and miles before these skills become second nature. Stay off of busy roads when you're perfecting these essential skills.
Conclusion:
This is a very general description of the differences & hazards related to riding a PF. Indeed, these were the questions that I had when I started riding penny-farthings. I now have thousands of miles experience riding PF's on the UK's busy dangerous roads. There was info apparently on Facebook, but being a FB Refusenik I couldn't access any of it.
If you're a road cyclist - or any type of cyclist - who's keen to take up cycling a PF, I've put together a comprehensive resource that's been peer reviewed by other experienced PF riders, one of which has 40 years PF experience, so it's righteous. For those keen to learn more about the fine points of the above, go to:
http://www.penny-farthing.org
It's not behind any required logins and universally accessible to all. Penny-farthings are epic bicycles, but to be fair they're also quite dangerous when you're a newbie. This site was conceived with the goal of helping folks stay safe while gaining the fundamental skills required to ride a PF - SAFELY.
PF riders are an eclectic bunch. We come from all walks of life and political persuasions, but we all find common purpose & fraternity in our love for these complex Victorian bicycles. We are a retired Royal Mail transportation manager, a gay doctor, former police officers, former special forces operatives, a few currently serving firefighters, a retired judge, a retired helicopter pilot, and an outstanding tyre guy who makes us all look like PF slackers. And others. All are keen to transfer our skills to help newbies learn to ride a PF safely so the tradition of these epic bicycles does not die out. There is no elitism or classism here; only love of olde worlde bicycles unites us all.
Comment: Sounds like riding a PF is a very bad idea and they are an abandoned evolutionary stepping stone best left as museum pieces. But I would imagine the view to pretty good up there. Is it actually worth it though?
Comment: @ChrisH Once you get the hang of staging your approach to the juncture/roundabout/traffic signal, it's not too bad. I ride my mount pegs approaching junctures where I don't have line-of-sight of on-coming traffic which gives me the option of either continuing into it if safe, or completely dismounting and halting if not safe to proceed. If you can pedal slowly to time your approach, you can generally avoid stopping. There's a video in this link of what I'm talking about: http://www.penny-farthing.org/direction-change/
Comment: That's pretty clear, thanks.  Then I guess once you've had some practice remouting is quicker than I imagine
Comment: @Bohemian I guess the same could be said for riding bicycles or even motorcycles on public roads in general; it's deadly out there. Riding Penny-Farthings though is a great experience and all of us who ride them agree that it's worth the risk. It's really weird: you cycle past people and they immediately smile. I have never seen any other machine capable of managing this feat. As well of course as making the rider themselves smile ;-)
Comment: One thing that would put me off on any realistic roads is the time taken to get going if you do have to stop for a junction, given small gaps or limited lines of sight.  I'd struggle to even get out of my road. Are there tricks to deal with that, or can you rely on a little more goodwill than a typical roadie?
Answer: I've not ridden a PF, but I have tried a tall bike where the saddle was roughly even with my head.  Both styles put you far out of reach of the ground.
The main problem is the gap in balance between Stopped and Moving.  On a regular bike, you push off and you're doing ~5 km/h within half a crank revolution.
Getting the confidence to do that on a taller bicycle takes some doing.  You simply cannot ride it slowly.   There is a basement-speed that you must get to in order to gain stability.
Easy Mounting - the lazy way to do it is use a handy fence, street light, a low wall or similar.  Clamber up the bike's frame using the steps in a PF or the frame of a tall bike, and get yourself in the saddle with feet on the pedals.  Push off from your support and pedal hard - you NEED to get to 5 km/h as fast as possible to get some steerage way. This is not a long-term good way to use the bike, just a way to get you moving in a space that has no obstructions or surprises.
Stopping - obviously when you stop you'll need to do so beside a support or somewhere you can rest a foot.  A traffic light or street light is great.  Trees are awful for support, and vehicles are a really bad idea too.   Or you have to do a quick dismount and stand on the ground.
Perhaps avoid roads completely until you're confident.  A pleasant horn is a good idea too.
Other issues:

Trees are suddenly annoyingly low.
Many kids and some adults are dumb-stuck and can simply stop in your way.
Pets are as bad as usual at getting in the way.
Gradients are very disconcerting, both going up and down.  Try and avoid any climbs or descents when learning.  Even gutter-crossings can throw the unexperienced rider.

Protection: A fall from that height can be unpleasant.   You might choose to wear rollerblading wrist guards.  If the bike's going down, try and step over the frame and get both feet under you for landing.  Avoid landing on your head, that's always a bad idea.
And have fun - its all about trying something new.
Comment: You shouldn't use a fence to mount a Penny-Farthing as you suggest in "Easy Mounting": If you can't mount a Penny-Farthing in a non-emergency situation, if you're confronted with a hazard while cycling it, the odds are 100% there won't be a fence to lean against to dismount.  You really need to learn mounting & dismounting without using a crutch like fences or posts.  Cycling a PF is not the chanllenge: it's the getting on & off bit that is the key skill to transition from riding a standard bicycle.
Comment: @F1Linux Totally fair point there.  Was only mentioned as a way for the new rider to get some saddle time without having to completely master the mounting skill, AND provides a way to stop and give some confidence.   When I tried the tall bike, it was in a large open park with a lot of empty space.  We used a light post to mount/unmount and a convenient portaloo on the other side as a foot rest.  Then Ross the Unicycle madman decided he could do a running mount, and achieved it on the third attempt.  That was a memorable day.
Comment: "open parks" can have unleashed dogs ;-). Cycling a PF isn't much different than a standard bicycle once you're on it- other than turning less sharply & avoiding debris which could obstruct the front wheel. Hence the topic was "skills required to transition to riding a Penny-Farthing".  Can't emphasize it enough: mounting & dismounting are fundamental skills which must be mastered before focusing on the cycling bit itself. When I learned to ride a PF, I just went in a loop mounting, turning around & dismounting, repeating it until I gained the muscle memory to locate the pegs.


Query Syntax by Drug Class

Question: I am interested in creating a dataset that only contains that class of drugs. I would prefer being able to search by the drug name, but entries for that field are masked. Does anyone know if I can search by and create a dataset by drug class?
Answer: I'm Violet Wren, the tech lead of the openFDA dev team. Which endpoint are you searching for this information? A link to an example search would be great and I can help further from there.

Query Syntax by Drug Class