How to access specific elements of an array?

Suppose I have two matrices A and x as follows:

x =

     1     2
     2     3

A =

     1     1     1     1
     1     1     1     1
     1     1     1     1
     1     1     1     1

Each row of x contains the row and column indices of an element of A that I would like to access and change. In the above example, I want to change the (1,2) and (2,3) elements of A. Suppose I want to set the value of these elements to 5. The command 'A([1 2],[2 3]) = 5;' produces A =

     1     5     5     1
     1     5     5     1
     1     1     1     1
     1     1     1     1

However, what I want is the following:

A =

     1     5     1     1
     1     1     5     1
     1     1     1     1
     1     1     1     1

In my actual code, A and x may have thousands of elements each. Therefore, I am wondering whether it is possible to do this without using a for loop?

Answer 1

[Star Strider]

One approach:

ix = sub2ind(size(A), x(:,1), x(:,2));              % Change Subscripts To Linear Index Vector
A(ix) = 5;

A =
     1     5     1     1
     1     1     5     1
     1     1     1     1
     1     1     1     1

[Karthik Nagarajan]

Thank you for the quick reply. Exactly what I was looking for!

[Star Strider]

As always, my pleasure!