How do I iterate over vector elements, but ignore elements which do not meet a condition?
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I have a piece of code, which I'm trying to make run faster. I've used the profiler and most of the time is spent on the following snippet:
for det = 1:N
if detect_vec(det)
result((det+1):(det+deadTime), m0, h) = zeros([1, deadTime]);
end
end
What this is doing is iterating over an array detect_vec which is binary data - each element is a 1 or a 0. If there is a 1, it then sets any other 1s following it to 0. deadTime is a variable which defines how many values after a 1 should be set to 0.
I'm sure there must be a way to make this more efficient; N is very large and so it makes sense that the profiler says the code spends most of its time here. I've tried using the find function by doing the following;
for det = find(detect_vec)
if detect_vec(det)
result((det+1):(det+deadTime), m0, h) = zeros([1, deadTime]);
end
end
This code runs without error but returns many more 1s than I'm expecting, and isn't really any quicker.
Any advice would be great.
4 Comments
dpb
on 11 Dec 2020
Unless the separation of elements in detect_vec is >deadTime you'll be resetting elements multiple times and moving the location of the string of zeros along with it.
Is this intended behavior? You could otherwise increment by the gap at least. Whether this reduces iterations or not would depend on the relative values and number of detection locations.
You may want to look at fillmissing with the 'MaxGap' option (if you have R2020b, I think is required).
Accepted Answer
More Answers (2)
Matt J
on 11 Dec 2020
Edited: Matt J
on 11 Dec 2020
e=zeros(1,deadTime);
I=conv( double(detect_vec~=0), [e+1,0,e] , 'same')>0;
result(I, m0, h)=0;
2 Comments
Matt J
on 11 Dec 2020
Maybe use FFTs to do the convolution, or maybe,
e=ones(1,deadTime);
I=conv( double(detect_vec~=0), [e,0] , 'same')>0;
result(I, m0, h)=0;
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