Assigining the pixel location

Question

I have the following matrix:

a =

     1     4
     6     4

After that, I created a zero matrix new of the same size of a:

new =

     0     0
     0     0 

I'm trying to do the following:

• assign the location (2,1) in a to the variable p
• for that location in new, I want to give it the value 1

For that, I did the following:

p=a(2,1);
new(p)=1;

But, I got the following:

In an assignment  A(I) = B, a matrix A cannot be resized.

It seems that also p=a(2,1); assigns the value at that location and not the location itself.

How can I solve this issue?

Thanks.

Answer 1

If you want the "location" you can use the linear index of that pixel:

p = sub2ind( size(a), 2, 1 );
new(p) = 1;