Operation without for loop
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I have two matrix.MAtrix A(250000x4)and MAtrix B(250000x4)
I have a function which result a scalar C.
C = myfunction(X,Y);
Now i want to pass each row of MAtrixA and MAtrixB to myfunction without using a for loop.
How to do it ?
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채택된 답변
Andrei Bobrov
2012년 1월 31일
Y = arrayfun(@(i1)myfunction(A(i1,:), B(i1,:)), 1:size(A,1))
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Sean de Wolski
2012년 1월 31일
Sure. Permute B so that it is [1x4x250000].
bsxfun(@myFunction,A,permute(B,[3 2 1]));
It's going to use a ton of memory and probably be slower though. Of course, it's still awesomer because it uses bsxfun( :-).
추가 답변 (1개)
Walter Roberson
2012년 1월 31일
You can make it look prettier using arrayfun(), but arrayfun() is just going to be doing the "for" loop internally.
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Walter Roberson
2012년 1월 31일
Often in such cases the best thing to do is rewrite the function so that it accepts arrays.
Note that "for" loops are not necessarily slow, especially in new versions. There is probably more overhead in calling myfunction all those times than there is in the "for" loop itself.
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