CODEWITHSUNDEEP
matlabmatrixmatrix-indexing
Stewie Griffin
Stewie Griffin

Reputation: 14939

Vector as column index in matrix

Given a matrix A (mxn) and a vector B (mx1) I want to create a vector C (mx1) in which each row element is the row element of A from a column indexed by B.
Is it possible to do this, without using loops?

A = [1 2; 3 4; 5 6];
B = [2 1 1].';

Then I want:

C = [2 3 5].';

Upvotes: 3

Views: 405

Answers (1)

Eitan T
Eitan T

Reputation: 32920

Convert the column subscripts of B to linear indices and then use them to reference elements in A:

idx = sub2ind(size(A), (1:size(A, 1)).', B);
C = A(idx);

(for more information, read the part about linear indexing in this answer).

Upvotes: 6

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