CSV spreadsheet files are suitable for storing tabular data in a relatively portable way.

The CSV format is flexible but somewhat ill-defined.

For present purposes, authors may assume that the data fields contain no commas, backslashes, or quotation marks.



Task

Read a CSV file, change some values and save the changes back to a file.

For this task we will use the following CSV file:

C1,C2,C3,C4,C5
1,5,9,13,17
2,6,10,14,18
3,7,11,15,19
4,8,12,16,20

Suggestions


 Show how to add a column, headed 'SUM', of the sums of the rows.
 If possible, illustrate the use of built-in or standard functions, methods, or libraries, that handle generic CSV files.



   data=: (','&splitstring);.2 freads 'rc_csv.csv'       NB. read and parse data
   data=: (<'"spam"') (<2 3)} data                       NB. amend cell in 3rd row, 4th column (0-indexing)
   'rc_outcsv.csv' fwrites~ ;<@(','&joinstring"1) data   NB. format and write out amended data