function [z,pz] = mgsum(x,y,px,py)
% MGSUM [z,pz] = mgsum(x,y,px,py)  Sum of two independent simple rv
% Version of 5/6/96
% Distribution for the sum of two independent simple random variables
% x is a vector (row or column) of X values  
% y is a vector (row or column) of Y values
% px is a vector (row or column) of X probabilities
% py is a vector (row or column) of Y probabilities
% z and pz are row vectors
[a,b] = meshgrid(x,y);
t  = a+b;
[c,d] = meshgrid(px,py);
p  = c.*d;
[z,pz]  = csort(t,p);