It's not pretty, and there might be better solutions, but you can use the function sub2ind
like this:
M(sub2ind(size(M),1:numel(s),s'))
質問
I have an MxN
matrix and I want a column vector v
, using the vector s
that tells me for each row in the matrix what column I will take.
Here's an example:
Matrix =
[ 4 13 93 20 42;
31 18 94 64 02;
7 44 24 91 15;
11 20 43 38 31;
21 42 72 60 99;
13 81 31 87 50;
32 22 83 24 04]
s = [4 4 5 4 4 4 3].'
And the desired output is:
v = [20 64 15 38 60 87 83].'
I thought using the expression
Matrix(:,s)
would've work but it doesn't. Is there a solution without using for loops to access the rows separately?
解決
It's not pretty, and there might be better solutions, but you can use the function sub2ind
like this:
M(sub2ind(size(M),1:numel(s),s'))
他のヒント
You can also do it with linear indexing, here is an example:
M=M'; s=s';
M([0:size(M,1):numel(M)-1]+s)