compare two matrix and keep only the elements in common

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Aude Rapet 2016-11-21

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评论： Aude Rapet 2016-11-22

Hi, I am a beginner in matlab, and I need to compare to matrix and then keep only the elements present in both matrix in my 1st matrix (s(1).r). For this I compare the first column of each matrix. I've read the documentation and tried to write a code with ismember:

Lia = ismember(s(1).r(:,1), res_select(:,1)) ;
for ind = length(s(1).r)-1 : -1 : 1
   if Lia(ind)==0 
    s(1).r(ind,:)=[];
   end 
end

I think something is wrong, because I am supposed to find 1987 elements in common and I found 1988...so close! Where is my mistake, or is there an easier way to do this? Thank you!! Aude

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Answer 1

KSSV 2016-11-21

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编辑：KSSV 2016-11-21

We don't have data to check your code. Note that, You need not to run a loop...simply use, s(1).r(Lia,:) to get the common elements.

As you have two sets and you want to pick the common elements, you can find intersection of both the arrays. Intersection gives you common elements. doc intersect.

Sometimes depending on the floating point numbers, ismember/ intersect may not work. That case, you need to fix a tolerance value and use ismemebrtol. doc ismembertol.