error when using fprintf

2012 2 20
2 个回答
6 次查看（30 天）

0 个投票

can anyone tell me where I'm going wrong here.
clear all
data = rand(365,1);
filename = fullfile('file','test.txt');
fid = fopen(filename,'w');
fprintf(fid,'%s\n',data);
fclose(fid)
I'm trying to save a column vector into a .txt file but get the error:
Error using fprintf
Invalid file identifier. Use fopen to generate a valid file identifier.
The error says that I need to use fopen but I have used it so I'm not sure why an error occurs!

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回答（2 个）

Walter Roberson
Walter Roberson 2012-2-20

1 个投票

Your fopen() is failing, but you are not checking for that.
Your code is attempting to create a file named "test.txt" in a directory named "file" relative to the current directory. Is that your intention? Does the directory exist?

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Richard
Richard 2012-2-20
yes that was my intention. The name of the directory wasn't actually called file neither is 'data' the actual data that i'm using, just an example.
When taking what was mentioned by image analyst into consideration and my poor example I now have:
clear all
data = rand(1,365);
filename = fullfile('C:\Users\Woolway\Documents\MATLAB','test.txt');
fid = fopen(filename,'w');
fprintf(fid,'%f\n',data);
fclose(fid)
This produces a .txt file but not as a column vector as shown in matlab, shouldn't \n account for this?
Walter Roberson
Walter Roberson 2012-2-20
You may need to open with 'wt' rather than with 'w' . 'wt' is for text files, and 'w' is for binary files.
Richard
Richard 2012-2-20
that works, thank you very much.

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Image Analyst
Image Analyst 2012-2-20

1 个投票

Try adding this line right before the fullfile() line
if ~exist('file', 'dir')
% The (badly named) folder called "file" does not exist.
% Create that folder.
mkdir('file');
end
Beyond that, you're opening a file not in text mode and then using a text format specifier (%s) to write out numerical data. What do you think that will do? Maybe you should use %f instead.

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Richard
Richard
2012-2-20

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