function [z,pz] = mgnsum(X,P)
% MGNSUM [z,pz] = mgnsum(X,P)  Sum of n independent simple rv
% Version of 5/16/96
% Distribution for the sum of n independent simple random variables
% X an n-row matrix of X-values
% P an n-row matrix of P-values
% padded with zeros, if necessary
% to make all rows the same length
[n,r] = size(P);
z  = 0;
pz = 1;
for i = 1:n
  x = X(i,:);
  p = P(i,:);
  x = x(find(p>0));
  p = p(find(p>0));
  [z,pz] = mgsum(z,x,pz,p);
end