Extract columns from matrix based on a vectors values

I want to extract the columns of a matrix A (mxn), based on a vector B's values into a new matrix C, meaning:

Which also should be dependent on B's dimensions (1xm):

For example:

A=[1,1,1,0;
   2,1,0,1];
B=[3,4];

Then C should be:

C=[1,0;
   0,1].

I want this to work for any dimensions of n and m.

I have tried:

C=A(:,B(1,1):1:B(1,size(B,2))) 

but it doesn't work for B=[3,1] since it takes column by column.

Thanks!

Answer 1

[Jon]

I think this should do it for you:

C = A(:,B)

[Tom Hagéus]

Thanks works now!

[Jon]

Glad this works for you. Please accept this answer so others with a similar issue will know an answer is available.

Answer 2

[dpb]

>> A=[1,1,1,0;
      2,1,0,1];
B=[3,4];
>> A(:,B)
ans =
     1     0
     0     1
>> B=[3,1];
>> A(:,B)
ans =
     1     1
     0     2
>> 

meets the description of the vector B.

If you mean for B to be all columns from B(1):B(2) inclusive, then you have to be more explicit in how you write the expression:

>> A(:,B(1):sign(diff(B)):B(2))
ans =
     1     1     1
     0     1     2
>> 

This will require that B always be a 2-vector and B(1)~=B(2).

[Tom Hagéus]

Thanks, A(:,B) solved it!