Using fprintf to print in text file

This is my script and I am trying to use fprintf to print sth in other file. This is the script I have currently and this does not change anything in my output.txt file. How can I print 'f' in the text file??

 function [] = words(input, output)

 fid = fopen(input, 'r');
 a = [];

 while ~feof(fid)
    line = fgetl(fid);
    e = lower(line);
    b = strsplit(e);
    a = [a b];
 end

 c = unique(a);
 e = transpose(c);
 f = string(e);

 kid = fopen(output, 'w');
 fprintf(output,'%s\n',f);

 end

Answer 1

[Cedric]

The first argument in the call to FPRINTF should not be the file name but the file handle that you get with FOPEN:

 kid = fopen(output, 'w');
 fprintf(kid,'%s\n',f);

Also, I don't know what f is, but it may not be a string. You'll have to check that. If it is a cell array of strings, you can STRCAT them or just update the call to FPRINTF as follows:

 fprintf(kid,'%s\n',f{:});

where f{:} develops f as a comma separated list (CSL). Finally, you have to close the file at the end:

 fclose(kid);

Answer 2

[OCDER]

New solution: works for words separated by non-letter characters (ex: dog, cat, "bird")

   function extractWords(input, output)

   fid = fopen(input, 'r');
   txtchar = fscanf(fid, '%c'); %use fscanf to save everything as char array, incl space
   fclose(fid);

   txt = unique(regexpi(lower(txtchar), '[a-z]+', 'match'));

   kid = fopen(output, 'w');
   fprintf(kid,'%s\n', txt{:});
   fclose(kid);

OLD SOLUTION - does not work for words followed by , . " (ex: dog, cat, "this")

   function extractWords(input, output)
   fid = fopen(input, 'r');
   txt = textscan(fid, '%s');
   txt = txt{1};
   fclose(fid);

   txt = unique(strrep(lower(txt), '.', '')); %Thanks Jan for this simpler code!

   %txt = cellfun(@(x) strrep(x, '.', ''), txt, 'UniformOutput', false');   
   %txt = unique(cellfun(@lower, txt, 'UniformOutput', false)); %get unique, sorted words, lower case   

   kid = fopen(output, 'w');
   fprintf(kid,'%s\n', txt{:}); 
   fclose(kid);

General suggestions:

• No need for function [] = words(...) if there's no output. function words(...) works.
• Use textscan to extract all words from a text file
• Use Matlab's concept of " comma separated list ", txt{:}, to print all cells at once via fprintf.
• Label variables to have meaning, instead of a, b, c, d
• Label functions with a verb so that you'll know in the future it's a function and not some word cell array. Ex: extractWords(input, output) is obvious it's a function that extracts words from input and saves to output. words(input, output) looks similar to an array of words, where words(1) and words(2) looks like a reference to the 1st word and 2nd word.

[Jan]

strrep and lower operate on cell strings directly:

   txtC = textscan(fid, '%s');
   txt  = txtC{1};
   fclose(fid);

   txt = strrep(x, '.', '');
   txt = lower(txt);

Thios is nicer and faster than the cellfun application.

[OCDER]

Thanks for this suggestion! I keep forgetting these work on cell arrays too. I edited the previous answer, and provided a new one as my prev answer did not handle words separated by comma, quotation, numbers, etc.