Matrix(Matrix)

I am a new MATLAB user and am unsure of what operation is being carried out by the below chunk of code.

a=[1 1;1 2]
b=[1;0;0;1]
b(a(:),:)

ans =
     1
     1
     1
     0

a(:)

^obviously gives the column vector of a.

(a(:),:) 

^selects all rows and columns in this column vector.

b(a(:),:)

^what does this chunk of code do?

Answer 1

[James Tursa]

The "a" values are simply being used as row numbers for indexing into b.

b(a(:),:)

= b([1;2;1;2],:)

which is equivalent to

[ b(1,:);
  b(2,:);
  b(1,:);
  b(2,:)]

=

1

0

1

0

Answer 2

[nada zaidi]

B=A(2 -3 2 -4)