Sum of number of pairs?

I have two columns x and y. Each contains only 8 values. These are numerical but are descriptive (nominal). I want to get an 8x8 matrix with the count of how many times a particular set happened.

For background info x and y are origins and destinations. Each row is a shipment and I need to know how many shipments between the origin and destination.

Small example (2x2):

x = a a a a b b b b b b
y = a a a b b b b a a a
M = [3 2;3 2]

[Azzi Abdelmalek]

What are your data and what is the result? How did you get the result?

Answer 1

[John D'Errico]

[~,~,xtags] = unique(x);
[~,~,ytags] = unique(y);

accumarray([xtags(:),ytags(:)],1)
ans =
     3     1
     3     3

I think you miscounted those combinations for your example.

[Sofia]

Woops! Thanks!