Question about ismember replacements

Hello, thanks for reading this,

I have a question about a very timely procedure in a MATLAB script I have. Something I have to do repeatedly is check for point indices in a global matrix, and my repetitive calls are getting to be very costly time-wise.

A rough snippet of the code I have is:

 l2 = ismember(randomgen_ptmx,bifPt, 'rows');
[maxval,ind] = max(l2);
counter = 1;
for i=1:length(randomgen_connMx)
    if ind == randomgen_connMx(i,1)
        dag(counter) = i;
        counter = counter+1;
    end
end

where bifPt is a 1x3 array, and randomgen_ptmx is a nx3 matrix. What I do in the first three lines is search for the index of the big point as it exists in the randomgen_ptmx matrix, then I take that index and dearch for where it is the first entry in a n1x2 matrix (randomgen_connMx).

So, a simple explanation is I want to see where the index of bifPt in the global matrix randomgen_ptmx is in the first column entry of randomgen_connMx. I check for this in a ismember function, but when I profiled my code my repetitive calls to ismember is by far the biggest time waste I have. Are there better ways to do this?

Thanks a lot for your advice!

Answer 1

[Brian]

Actually, I managed to solve this myself:

 bif_index = find(bifPt(1)==randomgen_ptmx(:,1) & ... bifPt(2)==randomgen_ptmx(:,2),1,'last'); 

 dag = find(bif_index == randomgen_connMx(:,1));

did everything I needed to do. Hope this helps anyone else with a ismember problem.