How can I extract specific columns of a Matrix

For example I have this matrix

A = [1 0 0 0;0 0 0 0;0 1 0 0;0 0 0 0]

I want just extract the columns that they have one, (in this matrix will be column 1 and 2), and then show it in another matrix. I want to do this function for a big matrix. so the question must be d = [1 0;0 0;0 1;0 0]

Thanks

Answer 1

[Cedric]

Here is an example

 >> A = [1 0 0 0;0 0 0 0;0 1 0 0;0 0 0 0]
 A =
     1     0     0     0
     0     0     0     0
     0     1     0     0
     0     0     0     0

 >> colId = any(A, 1)
 colId =
     1     1     0     0

 >> d = A(:,colId)
 d =
     1     0
     0     0
     0     1
     0     0

Putting all that together, you would perform the following operation:

 >> d = A(:,any(A,1)) ;