MATLAB: How to index a matrix with existing array

index

Hi all,
Imagine there is a m by m matrix, I'd like to extract the [p, q] element, while [p, q] is the output of some calculations. For instance:
K>> a = rand(3)
a =
      0.88517     0.098712      0.67973
      0.91329      0.26187      0.13655
      0.79618      0.33536      0.72123
K>> b = [2 3]
b =
     2     3
K>> a(b)
ans =
      0.91329      0.79618
Here b is the location, which should be the 2nd row, 3rd column. However, here Matlab gives the 2nd and 3rd element by column indexing. What I want is 0.13655.
I know I can use:
K>> a(b(1), b(2))
ans =
      0.13655
But this is manual, my matrix may have random dimension, so I prefer something like a(b), any ideas?

Best Answer

Simply use num2cell and sub2ind, then indices are not required:
>> c = num2cell(b);
>> a(sub2ind(size(a),c{:}))
ans =  0.13655
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