n=A(B) where A and B are matrices?

Hello, I just tried to do the following operation,

>> B=full(B)

B =

     5     1     8     3     2     8
     9     9     8     8     3     6
     1     1     1     4     2     5
     4     7     4     9     2     2

>> A=full(A)

A =

     1     8     2     6     5     9
     4     3     6     7     1     2
     2     5     3     7     3     8

>> A(B)

ans =

     3     1     6     2     4     6
     3     3     6     6     2     5
     1     1     1     8     4     3
     8     2     8     3     4     4

I would like to know what exactly has happened here. Thank you.

Answer 1

[David Sanchez]

A(B) returns the value of the B(ith) element of A. The elements are counted column-wise, what means than in your case: A(1) = 1; A(2) = 4; A(3) = 2; A(4) = 8; A(5) = 3; ... A(18) = 8;

Now, if you take the matrix B as index, you get back a matrix whose elements are the elements of A in the position determined by the value of the element of B:

B(1) = 5

then, the first element of A(B) = A(5) = 3.

B(2) = 9

then, the second element of A(B) = A(9) = 3

B(3) = 1

then, the second element of A(B) = A(1) = 1

and so on.

[Abhijith]

Thank you for your answer.