How can I make a smaller matrices from a bigger matrix?

When I want to make a bigger matrix from smaller one I use this method that I explain below:

C=[2 3 10]
A=[4 5 6;7 8 9;10 11 12]
B(C,C)=A

In this method every element of matrix A is put in matrix B in a special position that matrix C tells.

But now I have bigger matrix ( matrix B ) and I want to make smaller one which is matrix A with the help of matrix C again, exactly vise versa of what explained and done before. How can I do it? I love working with Matlab special feature in matrices more than using for loops in programming.

Answer 1

[Andrei Bobrov]

A = B(C,C);