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How to speed up this code?

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pietro
pietro on 23 Jan 2019
Answered: pietro on 24 Jan 2019
Hi all,
I have the following code that I need to speed-up:
a(1).a='a';
a(2).a='b';
a(3).a='b';
a(4).a='c';
output=(contains(cellstr(char(a.a),'b')))
the desidered output is:
output=[0 1 1 0]
In my case the size of a is [11'000x1], so the computation is pretty slow.
How can I speed up the code?
Thanks

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Accepted Answer

Guillaume
Guillaume on 23 Jan 2019
Your code would be much faster if you didn't so many unnecessary conversions. a.a is a comma separated list (which is bascially a cell array) which you convert to a char array and then split back into a cell array.
output = contains({a.a}, 'b')
does the same without any conversion.
It's not clear from your simple example if you really want to use contains (which check that 'b' is present anywhere within the char vector) or strcmp (which check that the char vector is exactly identical to 'b') which would be faster or even == which would be even faster but only work if all char vectors are just one character.
output = strcmp({a.a}, 'b') %faster than contains if whole string comparison is required
Other than that, there's not much option to speed this up.

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More Answers (1)

pietro
pietro on 24 Jan 2019
Thanks for the aswer. Now the code is really fast. I have to use contains, because I have to search for string patterns.

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