I have a txt file containing a Matrix separated by commas. I would like to add a comma after the last column on every row.

I have a .txt file containing >200'000 rows and 12 columns separated by commas (only numbers, no characters). I would like to add a comma after the last column on every row without adding any values in a 13. column. (example below).

example of what I have:

1,2,3,4,5,6,7,8,9,10,11,12

1,2,3,4,5,6,7,8,9,10,11,12

example of what I am trying to get:

1,2,3,4,5,6,7,8,9,10,11,12,

1,2,3,4,5,6,7,8,9,10,11,12,

Thank you already for your time.

Answer 1

[dpb]

data=readlines('yourfile.txt');                         % read file as string array
data=data(strlength(data)>0);                           % save only non-empty lines
data=strcat(data,",");                                  % catenate "," on end
writematrix(data,'yournewfile.txt','QuoteStrings',0)    % write back out, don't quote

[Andri Graf]

It works very nicely, thank you. For some reason it adds a comma in a newly created row at the bottom of the txt file, which is no big problem though.

[dpb]

That's an unwanted artifact of readlines that I forgot to put in the cleanup for...sorry about that.

I may posit this as a "quality of implementation" issue in readlines; I don't believe it should do that although I suppose it probably depends on whether the file has an ending \n or not.

[dpb]

I did just check -- it is, indeed, whether or not there is that last newline or not.

The above fix will remove it if is there in the original; leaving it out will produce the extra ','; a little extra logic could have both by testing if there is a blank line and only appending the ',' to those lines that are longer.

data=readlines('yourfile.txt');                         % read file as string array
ix=strlength(data)>0;                                   % find non-empty lines
data(ix)=strcat(data(ix),",");                          % catenate "," on end
writematrix(data,'yournewfile.txt','QuoteStrings',0)    % write back out, don't quote

[Andri Graf]

great. thank you for your help!