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Changing save name for text file

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Leon Caldeira
Leon Caldeira on 27 May 2014
Edited: Geoff Hayes on 27 May 2014
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);
  1 Comment
Geoff Hayes
Geoff Hayes on 27 May 2014
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

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Answers (3)

Sara
Sara on 27 May 2014
Use:
S=strcat(cd,'\Results\',[answer,'.txt']);
  3 Comments
Leon Caldeira
Leon Caldeira on 27 May 2014
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'

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Roberto
Roberto on 27 May 2014
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
  1 Comment
Leon Caldeira
Leon Caldeira on 27 May 2014
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.

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Geoff Hayes
Geoff Hayes on 27 May 2014
Edited: Geoff Hayes on 27 May 2014
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.

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