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Question

I have a whole lot (hundreds of thousands) of rather large (>0.5MB) files, where data are numerical, but with a comma as decimal separator. It's impractical for me to use an external tool like sed "s/,/./g". When the separator is a dot, I just use textscan(fid, '%f%f%f'), but I see no option to change the decimal separator. How can I read such a file in an efficient manner?

Sample line from a file:

5,040000	18,040000	-0,030000

Note: There is a similar question for R, but I use Matlab.

Answer

My solution (assumes commas are only used as decimal place holders and that white space delineates columns):

fid = fopen("FILENAME");
indat = fread(fid, '*char');
fclose(fid);
indat = strrep(indat, ',', '.');
[colA, colB] = strread(indat, '%f %f');

If you should happen to need to remove a single header line, as I did, then this should work:

fid = fopen("FILENAME");                  %Open file
indat = fread(fid, '*char');              %Read in the entire file as characters
fclose(fid);                              %Close file
indat = strrep(indat, ',', '.');          %Replace commas with periods
endheader=strfind(indat,13);              %Find first newline
indat=indat(endheader+1:size(indat,2));   %Extract all characters after first new line
[colA, colB] = strread(indat, '%f %f');   %Convert string to numerical data