MATLAB: How to index into a 2D matrix using two equal length R and C vectors

indexingMATLAB

I have a 2D matrix rho, and two vectors of indices R and C. How do I use R and C to index into rho?
>> rho=d
rho =
      16     2     3    13
       5    11    10     8
       9     7     6    12
       4    14    15     1
>> R=[1 2]; C=[ 2 3];
i.e I want to obtain rho(R(1), C(1) ..etc

Best Answer

You can use a combination of linear indexing and the function sub2ind to index into rho:
>> rho=d
rho =
      16     2     3    13
       5    11    10     8
       9     7     6    12
       4    14    15     1
>> R=[1 2]; C=[ 2 3];
>> ind = sub2ind(size(rho), R, C);
>> rho(ind)
ans =
       2    10
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