What does the syntax matrix(vector) mean?
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I'm reviewing some code written by someone else, and it includes a line of the format:
a = m(v)
where m is a matrix and v is a vector. It's unclear to me exactly what operation this is performing. At first, I thought it was matrix multiplication, but the matrix does not have the proper dimensions to operate on the vector. The matrix is 1006x321, and the vector is 143x1. The output of this operation, a, is also a 143x1 vector. Since it can't be proper matrix multiplication, I really don't know what operation is being performed here. What exactly does this syntax mean?
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Voss
2024-7-17
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Raven
2024-7-17
You're welcome!
Here's an example to illustrate indexing a matrix with a vector:
m = reshape(100+(1:27),[],3)
v = 1:2:15 % a vector containing the odd numbers from 1 to 15
% a will contain the 1st, 3rd, 5th, ..., 15th elements of m.
% note that the counting goes down the first column of m first, then
% continues down the second column, and so on.
a = m(v)
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