fprintf use with error

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Rigo ZOO 2022-8-4

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https://ww2.mathworks.cn/matlabcentral/answers/1773885-fprintf-use-with-error

评论： Rigo ZOO 2022-8-4

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

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Answer 1

Star Strider 2022-8-4

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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!

.

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Rigo ZOO 2022-8-4

Star,

Great, thanks again it works.

Cheers

Star Strider 2022-8-4

As always, my pleasure!

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Answer 2

Fangjun Jiang 2022-8-4

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编辑：Fangjun Jiang 2022-8-4

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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

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Rigo ZOO 2022-8-4

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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Answer 3

Image Analyst 2022-8-4

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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);