Improving Efficiency of Find Algorithm
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Hello,
I am aware that logical indexing is much faster than the usage of the find function, in specific instances. I'm wondering if there is a way to improve the following algorithm - I'm not quite sure how to use indexing (if possible) in this situation.
What I have is a matrix of ascending values, though some of those values may be repeated (specifically, I have millions of ascending timestamps with many repeated). I am then seeking the start and end indices of a window that is between time X and Y.
Here is an example of the algorithm that I currently have implemented:
myDataTimestamps = [10 20 30 30 30 40 50 60 60 60 70 70 80 90];
window_start_time = 30;
window_end_time = 80;
start_index = find(myDataTimestamps >= window_start_time,1,'first');
end_index = find(myDataTimestamps <= window_end_time,1,'last');
Is there a way to improve the speed of this code and still return the same start_index of 3 and end_index of 13?
Much appreciated!
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回答(2 个)
Cris LaPierre
2021-8-19
This approach may only work for this simple case, but here's a way to do it using max/min.
myDataTimestamps = [10 20 30 30 30 40 50 60 60 60 70 70 80 90];
window_start_time = 30;
window_end_time = 60;
% find start/end index
ind = 1:length(myDataTimestamps);
wind = myDataTimestamps==window_start_time | myDataTimestamps==window_end_time;
start_index = min(ind(wind))
end_index = max(ind(wind))
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