Bhilding new matrix with selected index number

Suppose I have a matrix a:

a = [9;1;3;2;5;6;8;1;2;5;8;2];

And I have another matrix b which is like some selected index number of matrix a:

b = [4;6;1]; % for example 4 means forth row in matrix a which is 2 here

So, I need to have a new matrix c in that way present those rows in matrix a which are indicated in matrix b and others array be equal to 0:

c = [9,0,0,2,0,6,0,0,0,0,0,0]; % for example first array is 9 because the first row is (1) is in the matrix b and the value is equal 9 because first row in matrix a is 9.

Answer 1

[Orion]

just use b as an index vector :

a = [9;1;3;2;5;6;8;1;2;5;8;2];
b = [4;6;1];

c=zeros(1,length(a));
c(b) = a(b);