Using textread and strfind to extract lines of data

2012 11 27
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I have used textread to load a data file into memory. From here, I want to extract specific lines that contain a particular string. I imagine I can do this with strfind, but the documentation indicates it will only return the start index of the string. How can I extract the whole line of data?

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Jonathan Epperl
Jonathan Epperl 2012-11-27
You probably used textread to load data into a variable, and if you didn't, then you should do so. Also you should give some more detail: What does your data look like, what do you mean by 'line', is your data separated by line breaks?

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Paul Huter
Paul Huter 2012-11-27

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This is what I came up with:
fo = fopen('out.dat', 'wt')
t = textread('input.dat', '%s', 'delimiter', '\n', 'bufsize', 1048576);
c = 1;
for z = 1:1:length(t)
s = strfind(t{z}, string)
if ~isempty(s)
fprintf(fo, t{z});
fprintf(fo, '\n');
c = c + 1;
clear s
end
end
fclose(fo);
Seems to work quite well.

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Jan
Jan 2012-11-27
There is no need to "clear s". "fprintf(fo, t{z})" will lead to errors, if the string contains a % character. Better:
fprintf(fo, '%s\n', t{z});

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