Azzera filtri
Azzera filtri

How to speed up this code?

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pietro
pietro il 23 Gen 2019
Risposto: pietro il 24 Gen 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

Risposta accettata

Guillaume
Guillaume il 23 Gen 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.

Più risposte (1)

pietro
pietro il 24 Gen 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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