How can turn two indexing vectors into a corresponding matrix that counts how many locations that point has been hit?

Basically if I have two corriponding vectors, x and y say,

x = [1;1;2;1];

y = [1;1;1;2];

I want to return a matrix that represents how many times that point was referenced in the indexing matrix. For our example it would be,

2 1

1 0

Because there are 2 (1, 1) in the indexing vectors so a 2 is displayed in the matrix and because (2,2) was never in the vectors, it displays a zero

I've tried

matrix = zeros(2, 2);

matrix(x, y) = matrix(x, y) + 1

but it returns

1 1

1 1

How can I turn two vectors like these into a matrix that shows me how many times the combomation of x and y shows up in the vectors.

Answer 1

[BobH]

The diagonal of a matrix is those elements whose subscripts are (1,1), (2,2), etc

s = sparse(x, y, 1)
s =
   (1,1)        2
   (2,1)        1
   (1,2)        1
   
full(s)
ans =
     2     1
     1     0
     
d = full(diag(s))
d =
     2
     0

[Steve Le]

Thank you so much! This worked perfectly; I was trying to do stuff with scatter too but this was much simpler.

Answer 2

[Steven Lord]

See the histcounts2 function.