How to change specific number in a specific line in text file?

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ss 2019-4-25

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https://ww2.mathworks.cn/matlabcentral/answers/458600-how-to-change-specific-number-in-a-specific-line-in-text-file

评论： Walter Roberson 2019-4-30

I want to change a specific number in line number (91) from a text file. Line 91 is: a=c+d*1.5. I need to change 1.5 with some other number. But the problem here is 1.5 is not constant, it keeps on changing. So, I want a general code that changes any number instead of 1.5 as well.

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Answer 1

Walter Roberson 2019-4-25

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https://ww2.mathworks.cn/matlabcentral/answers/458600-how-to-change-specific-number-in-a-specific-line-in-text-file#answer_372336

在 MATLAB Online 中打开

in_filename = 'YourInputFileNameGoesHere.txt';
out_filename = 'YourOutputFileNameGoesHere.txt';
S = regexp(fileread(in_filename), '\r?\n', 'split');
if isempty(S{end}); S(end) = []; end   %regexp often introduces an empty trailing field
S{91} = sprintf('a=c+d*%g', NewValue);
fid = fopen(out_filename, 'wt');   %or 't' instead of 'wt' if you are not using windows
fprintf(fid, '%s\n', S{:});
fclose(fid);

This code might alter the detail of whether the file ends in a newline, or if instead it just ends (either of which are valid for text files.)

It is not recommended that you write to the same output file as your input file: if something were to go wrong then you would have lost the input file. (But if you are sure you can recover from that...)

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Answer 2

ss 2019-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/458600-how-to-change-specific-number-in-a-specific-line-in-text-file#answer_372458

Text in line 91 is a=c(d)*1.5 ; i.e. c(d) implies that c as a function of d. I need to keep on changing 1.5 only for multiple times with different values.