Count number of rows that meet criteria based on elements in other rows

Hello. How can one count the number of rows based on the elements in the columns? For example, if we have the following matrix:

3 0 0 2

5 0 0 2

2 0 1 2

2 0 1 2

1 1 1 3

4 1 0 2

3 1 1 2

1 1 1 3

5 1 0 1

4 1 1 1

How can we count the number of rows that have number 2 in the first column and number 1 in the third column? I guess one should use 'length' right? Thanks!

Answer 1

[Voss]

nnz(A(:,1) == 2 & A(:,3) == 1)
% 1st column is 2 & 3rd column is 1

where A is your matrix