Can I ask for authorship/acknowledgement for writing small data analysis program for a large study? Earlier this year I entered into a high-profile molecular biology lab and started doing wet lab work (I am an undergraduate). Knowing that I have a computational background, my PI asked that I also help with a project that had been conducted over the last two years and was nearing its completion. I was told that if I made enough of a contribution that I could be listed as a coauthor. I wrote a program for the post-doc that is leading this project and used it to analyze the validity of part of his data. The most current (nearly final) version of the project's manuscript that is being passed around the lab unfortunately don't have my name anywhere on it, even though my code is listed in the supplementary information section.

I have always heard that you should get an authorship on a paper if your work resulted in a figure or sizable part of the discussion. My contribution to this project only slightly altered one figure, ensured the figure's validity, and got about 2 sentences in the discussion. My relationship with my lab and my PI especially is very important to me (I would love to continue my work here for at least another 2 years), so is it worth asking for a co-authorship, or at least an acknowledgement? Would doing so be inappropriate given my relative contribution (a month vs. 2 years) and status as an undergraduate in the lab?
Asking whether a contribution merits acknowledgement or co-authorship is always appropriate, as long as it is done in a professional and non-confrontational way.

The answer may be "no," but it's certainly worthwhile to ask. (And if the answer is "no," at least you have learned something about standards for authorship and acknowledgement in your lab/field.)