replace the b-th row and >30-th column of a by a-30
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Chaoyang Jiang
am 1 Apr. 2018
Bearbeitet: Walter Roberson
am 1 Apr. 2018
I want to replace the b-th row and >30-th column of a by a-30. How to make the following code more efficient within one line? Thank you!
a=randi(100,[100,100]);
b=randi(100,[30,1]);
for i=1:length(b)
a(b(i),30:end)=a(b(i),30:end)-30;
end
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Walter Roberson
am 1 Apr. 2018
There is no more efficient version for that.
I am not saying that it cannot be done in vectorized form: it can be done in vectorized form. I am saying that you need to make extra calculations and involve extra memory in such a way that the for loop is likely to be more efficient. Especially since duplicate b values are possible so you are going to be affecting the same location multiple times.
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