Matlab : how to get M(1,2) from vector v=[1,2]?

Question

Say I have:

M = [1, 2; 3, 4]
v = [1, 2];

M(v) gives [1 3] but I want to get is M(1, 2) = 3.

Is there a way to do it? Of course, I could do M(v(1), v(2)) but I need the thing to work for M an N-dimensional array and v a vector of length N.

Thanks very much

`M(1,2)` addresses the 2nd column of the 1st row of `M` which is `2`. Why do you want that expression to return `3` ? I'm not sure I understand your question. — High Performance Mark, Jun 05 '13 at 13:42
Sorry it was M(1,2)=2. I found the answer to my question in the topic proposed by Eitan : V=num2cell(v) and then M(V{:}). Thanks very much — JuliaR, Jun 05 '13 at 13:58

score 1 · Answer 1 · answered Jun 05 '13 at 13:42

1

If your goal is to get values from M, I would use M(sub2ind(size(M),v(:,1),v(:,2))) this will work for vector version of v nicely.

answered Jun 05 '13 at 13:42

emoberg

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bdecaf · Answer 2 · 2013-06-05T14:06:55.303

0

You could use how Matlab expands cell

M = [1, 2; 3, 4]
v = {1, 2}
M( v{:} )

( you can transform v with v_cell=num2cell(v) )

edited Jun 05 '13 at 14:06

answered Jun 05 '13 at 13:54

bdecaf

4,652
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Matlab : how to get M(1,2) from vector v=[1,2]?

2 Answers2