Index multiple elements in a vector using logical indexing

Hi, I want to use logical indexing to "grap" some elements from a vector. Normally if you're only looking for a single element, you could use the "find" function, for example:

A = [1 2 3 4 5 6];

B = 2;

C = [5 6 7 8 9 0]

D = C(find(A==B));

or use something like: D = C(A==B);

But now I am interested in finding multiple elements in A. So B becomes a vector in this case. For example:

A = [1 2 3 4 5 6];

B = [2 4];

C = [5 6 7 8 9 0]

I thought I could do something simular as in the upper case, by writing something like:

D = C(A==B). But apparently this does noet work.

Can anyone help me? Thanks a lot in advance!

[Sean de Wolski]

Very well written question, you get a vote!

[Matt Tearle]

Indeed! Good question, and good answers. A good community exchange all round!

(It was a Q&A of two halves, the comment with the most votes won, but MATLAB Answers was the real winner on the day. Ahhh, my cliche-o-matic is stuck...)

Answer 1

[Sean de Wolski]

Oleg's way is probably faster, but also:

D = C(any(bsxfun(@eq,A.',B),2))

[Rob]

Thanks a lot to both of you.

I was not aware of the "ismember" function, but this works indeed.

Thanks!

Answer 2

[Oleg Komarov]

For comparison with multiple elements:

D = C(ismember(A,B))

Also, avoid to use find when you don't need the coordinates.

Answer 3

[Vasileios Siomos]

This is an awesome trick thanks a bunch guys