Changing save name for text file

I am having issues about changing the name of a file using the fprintf/fileID function. When I try to input a string in the fileID, I get the "invalid filname" error.

Here is the function:

S=strcat(cd,'\Results\',answer,'.txt');

fileID=fopen(answer,'w');

fprintf(fileID,'%9s %9s\r\n','Fixation','Duration (ms)');

fprintf(fileID,'%10.5f %10.5f\r\n',Sc);

fprintf(fileID,'\r\n %10s\r\n','Total time');

fprintf(fileID,'%10.5f',Tt);

fclose(fileID);

[Geoff Hayes]

What is answer defined to be? Why define S and then not use it? If I try to run the above with default values for answer, Sc, and Tt then it works fine. Before you try to write to file, the code should check to see if the file identifier is valid:

 fileID = fopen(S,'w');
 if fileID > 0
   % do stuff

   % close file
   fclose(fileID);
 else
  fprintf('Error - could not open file %s\n',S);
 end

Answer 1

[Sara]

Use:

S=strcat(cd,'\Results\',[answer,'.txt']);

[Leon Caldeira]

Sara, it did not work. In fact, that 'S=strcat...' wans't necessary. My biggest problem is the 'Invalid filename' from the 'fopen' function.

Thank you anyway!

[Sara]

I guess the answer could be

fileID=fopen([answer,'.txt'],'w');

given how you were creating S.

[Leon Caldeira]

It didn't work again. Here's the error log:

??? Error using ==> fopen

Invalid filename.

Error in ==> EyeTracker at 226

fileID=fopen([answer,'.txt'],'w');

This is how I get the 'answer' string:

answer =

    'Leon'

Answer 2

[Roberto]

possible causes:

• answer contains invalid charater(s) for a file name
• more or less about the same error but the invalid character comes from CD (most comun error: current folder might contain spaces e.g. c:\my folder\ ).

Possible solutions:

• change the current directory to one with no-spaces in the path like C:\myfolder\
• read some solutions here

[Leon Caldeira]

Roberto, thank you for the answer.

About the directory path, when I use the default option (inputing a text to the filename) there's no problem. But when I input a variable string, it comes with the error. Also, I tried with no invalid characters and it did not work.

Answer 3

[Geoff Hayes]

Given your comment as to the return value for answer in Sara's response to your question, I almost think that answer is a cell array rather than a string. Just prior to evaluating

 fileID=fopen([answer,'.txt'],'w');

type in the command window

 [answer,'.txt']

and

 class(answer)

What is returned? If I type the following answer initializations in my command window I see

 >> answer = 'Leon'

 answer =

 Leon

 >> answer = {'Leon'}

 answer = 

    'Leon'

The second matches your return value. If it is indeed a cell array, then either replace with the string equivalent OR access the string value via answer{1} as a string must be passed as an input to the fopen function.