Logical indexing with matrix issue

2 views (last 30 days)
Senaasa
Senaasa on 27 Aug 2014
Commented: Senaasa on 27 Aug 2014
I ran into this issue writing a program using logical indexing. Suppose you have
A=ones(32,10);
M=zeros(32,10);
N=ones(1,10);
for i=1:32;
M(i,:)=N;
end
M=logical(M);
C=A(M);
Why is C a 320x1? Shouldn't it be equal to A since the logical is all 1's? Thanks, Charles

Accepted Answer

Yu Jiang
Yu Jiang on 27 Aug 2014
Edited: Yu Jiang on 27 Aug 2014
This is the intended behavior of Logical indexing. For example,
A = [1 2; 3 4];
Then, A(logical([1,1;1,1])) will return A(:), which is equal to
[1;
3;
2;
4].
And A(logical([1,0;0,1])) will return
[1;
4]
You can find more examples via the following link
  3 Comments
Senaasa
Senaasa on 27 Aug 2014
Thanks for your quick replies. I guess I've only ever used 1 row when using logicals, so I never noticed this issue.
Thanks for your help

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by