How to extract non-vertical column from matrix in Matlab
I have matrix A and a vector b, which specifies column index of the element to be extracted for each corresponding row of the matrix.
For example,
A = [1 2 3
4 5 6
7 8 9]
b = [1 3 2]'
I'd like to have c = [1 6 8]'
o开发者_JS百科n output. How to achieve this?
I tried A(:, b)
, but it doesn't work as I need.
There may be a more elegant solution, but this works:
b = [1 3 2]';
[rows, cols] = size(A);
A(sub2ind([rows cols], [1 : rows]', b))
As an alternative to @dantswain's solution, you can go to the linear indices directly, assuming you're always selecting from the columns:
r = size(A,1);
A( (1:r).' + (b-1) * r)
This will be faster, but not necessarily clearer.
Unfortunately, there isn't an elegant solution.
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