Replace repeated pattern in text file

Hi guys,

I have a .txt file where the string param is present in the form param1, param2,param3,....

What I would like to do is replace each of this param pattern with a different value. let's say if I have param1, param2 and param3 I want to replace these with three different values contained in a vector. I have tried with the following code: %%%%%%%%%%%%%

fin = fopen(['a.op4'],'r'); fout = fopen(['b.op4'],'wt');

   for j = 10:16
  while ~feof(fin)
    s = fgetl(fin);
    s = strrep(s,['param',num2str(j)],num2str(values(j)));
 fprintf(fout,'%s\n',s);

    end
%%%%%%%%%%%%%%%%       
But in this way it only replaces the value at param10 (first vakue of j). Any idea why?

Thanks!

Answer 1

[Guillaume]

You're trying to loop over two different things at once. Much simpler:

filepath = 'c:\somewhere\somefile.extension';
filecontent = fileread(filepath);  %read the whole file at once rather than line by line
for paramvalue = 10:16
    filecontent = strrep(filecontent, ['param',num2str(paramvalue)], num2str(values(paramvalue)));  %replace each parameter
end
%write the file back:
fid = fopen(filepath, 'w');
fwrite(filecontent);
fclose(fid);

You could also completely eliminate the loops by using a dynamic regular expression:

filepath = 'c:\somewhere\somefile.extension';
filecontent = fileread(filepath); 
%replace param10 - param16 at once with values(10)-  values(16):
filecontent = regexprep(filecontent, 'param(1[0-6])', '${num2str(values(str2double($1)))}');
%... save file

[salvor]

I get the error Subscript indices must either be real positive integers or logicals when I use strrep

[Guillaume]

Was that before or after I edited my answer to correct the mistake of using j instead of paramvalue inside the loop?

[salvor]

It works. The only issue is that the syntax of the file is slightly changed. So when param is replaced, the new number is not aligned with the others in the column

[Guillaume]

If you want the replacement string to be padded with spaces to be the same length as the original you can use, assuming that values is all integers:

filecontent = regexprep(filecontent, 'param(1[0-6])', '${sprintf(sprintf(''%%%dd'', numel($0)), values(str2double($1)))}')

Quite a mouthful of a replacement expression! Or since, the length of 'paramxx' is always the same, you could use the simpler:

    filecontent = regexprep(filecontent, 'param(1[0-6])', '${sprintf(''% 7d'', values(str2double($1)))}')

Adjust the sprintf format string as appropriate if values are not integer. You can had a format string the same way for the strrep option if you wish.