MATLAB: Fprintf specific column from multiple text files to one csv sheet

fprintfloop

Hi all, I previously wrote a short simple script to copy the third column of a text file to a new csv sheet (as shown below).
fid = fopen('pvt-results_1496-023B.txt','r');
parameters = textscan(fid, '%s%s%s\n','HeaderLines',4, 'Delimiter','\t');
fclose(fid);
gid = fopen('pvtsort.csv','wt');
fprintf(gid,'%s\n','Trail');
for k = parameters{1,3}
    i = 1:length(k)
    fprintf(gid,'%s\n',k{i})
end
fclose(gid)
So this worked fine. Now I'm trying to loop this script in order to copy the third column from multiple text files and put them all on a single csv sheet with headers (Trail [incremental numbers for each additional column]). My .m file is in the folder with all text files (same # of headerlines & columns, different # of rows), but I got stuck after loading multiple text files with
 fid = dir('*txt')
 for i = 1:length(fid)
    files(i) = fopen(fid(i).name);
    fid(i).values = textscan(files(i), '%s%s%s\n','HeaderLines',4, 'Delimiter','\t');
    fclose(files(i));
end
gid = fopen('pvtsort.csv','wt');
So I was trying to fprinf the third column from multiple text files to 'pvtsort.csv' but keep getting the error "Error using fprintf. Function is not defined for 'cell' inputs." So I tried loading the files differently using numel instead of length:
    for k = 1:numel(fid)
         pvt = fopen(fid{k},'r');
         content(k) = textscan(pvt,'%s%s%s\n','HeaderLines',4,'Delimiter','\t');
         data{k} = content{3};
         fclose(pvt);
     end
And got "Cell contents reference from a non-cell array object. " I guess I'm loading the txt files incorrectly here with the dir() function, which is why I can't even begin copy anything from the files, let along the specific column. When I tried to load the 16 txt files in my folder with fid = dir('*txt'), it throws the following info fid =16×1 struct array with fields:
  • name
  • date
  • bytes
  • isdir
  • datenum
I think the struct array is the issue here? Perhaps I should not use fprintf function to copy a string of data from multiple txt files onto a csv?
Pointers appreciated.

Best Answer

"Error using fprintf. Function is not defined for 'cell' inputs."
Indeed it isn't; must cast to character array...
fidO=fopen('pvtsort.csv','wt');  % open the output file
d = dir('*txt');  % 'fid' sounds too much like a file handle, not a directory listing...
for i = 1:length(d)
  fid=fopen(d(i).name);  % don't need the input file but once; no array
  values=textscan(fid,'%*s%*s%s','HeaderLines',4, 'Delimiter','\t');  % read only the 3rd column
  fid=fclose(fid);
  % now write the data to the new file; must loop for character data
  for j=1:length(values)
    fprintf(fidO,'%s\n',values{i});   % note "the curlies" to dereference cellstr to char
  end
end
fidO=fclose(fidO);
If you want a header line first, write it after opening the output file before starting the loop over the input files. end
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