How to vectorize writing to a txt file

Question

esbolico 2013-4-24

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https://ww2.mathworks.cn/matlabcentral/answers/73402-how-to-vectorize-writing-to-a-txt-file

采纳的回答： Cedric

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Hi there,

I have to write a function in matlab to create a txt file with the following format:

(x(1),y(1)),(x(2),y(2)),...(x(end),y(end))

I have the following piece of code (whre L is the length of vectors x and y)

for r=1:L;fprintf(fileOutput,['(',num2str(time(r)),',',num2str(signal(r)),'), ']);end

which obviously does the trick but I was wondering if anybody knows how to vectorize the expresion so that it runs much faster.

Any help will be welcomed!!

Thank you!

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Answer 1

Cedric 2013-4-24

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编辑：Cedric 2013-4-24

在 MATLAB Online 中打开

You could go for something like this:

 buffer = sprintf('(%f,%f),', [time; signal]) ;    % FormatSpec repeated.
 buffer(end) = [] ;                                % Remove extra ','.
 fid = fopen('output.txt', 'w') ;
 fwrite(fid, buffer) ;
 fclose(fid) ;

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Answer 2

esbolico 2013-4-24

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Dear Cedric,

thank you very much for you solution. Certainly it is a very clever solution and my program now runs hundreds of times faster. I did not even now the sprintf function, thank you for introducing it to me!

Regards

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Cedric 2013-4-24

Dear Esbolico,

The interesting "thing" with SPRINTF and FPRINTF, is that they will repeat the format (here '(%f,%f),') as many time as needed to print all elements of the array(s) that are given to them. It is certainly useful when you want to avoid writing loops. I'm glad it helped!

Regards

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