fprintf use with error

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Rigo ZOO
Rigo ZOO on 4 Aug 2022
Commented: Rigo ZOO on 4 Aug 2022
Hi,
I am getting warning with fprintf function in my script as specify below, I reallly don't how to figure out. I am a new matlab user
Thanks for your help
fprintf(fileID, " pointList.append(eval('(%s)' %line.strip())))\n");
error / warning : The format might not agree with the argument count

Accepted Answer

Star Strider
Star Strider on 4 Aug 2022
It looks as though you want to print a percent (%) sign.
Try this —
fileID = 1; % Print To Command Window
fprintf(fileID, " pointList.append(eval('(%s)' %%line.strip())))\n", 'Hi, There!');
pointList.append(eval('(Hi There!)' %line.strip())))
In the fprintf documentation see the formatSpec section and specifically Text Before or After Formatting Operators (no direct link to it) to understand how to do this correctly.
I have no idea what the string is supposed to be, so I created one to test the code!
.
  5 Comments
Star Strider
Star Strider on 4 Aug 2022
As always, my pleasure!

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More Answers (2)

Fangjun Jiang
Fangjun Jiang on 4 Aug 2022
Edited: Fangjun Jiang on 4 Aug 2022
use single quote mark, not double quote mark
a=1.2;
fid=1
fid = 1
fprintf(fid, 'this is my number %f', a)
this is my number 1.200000
  1 Comment
Rigo ZOO
Rigo ZOO on 4 Aug 2022
Thanks Fangjun,
But this option doesn't work either, I have already a simple quote '(%s)' . This option simple generte Invlaid syntax error.
Cheers

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Image Analyst
Image Analyst on 4 Aug 2022
The problem is you're using %s but not passing in any string after the format string. It needs to be of this form
fprintf(fid, 'stuff blah blah %s more stuff.\n', yourString);
The fprintf is seeing %s but not seeing yourString. Essentially you have
fprintf(fileID, " stuff %s more stuff\n");
as far as the mlint syntax checker is concerned. What is really wants to see is
fprintf(fileID, " stuff %s more stuff\n", yourString);
What you should do is this:
% Evaluate the expression with the hated eval
someNumber = eval(someString);
% Say someNumber is 5 and you'll use that as an index to the pointList.append array
yourString = sprintf(' pointList.append(eval(%d) %%line.strip())))\n', someNumber)
% Now write that string to the file.
fprintf(fileID, "%s\n", yourString);
  1 Comment
Rigo ZOO
Rigo ZOO on 4 Aug 2022
Thanks Image Analyst,
This method works as well
Cheers

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