function pmf=mfpascal(r, p) 
% mfpascal(r, p)  generates a Pascal pmf with parameters r and p 
if p<=0 | p>=1 
   error('invalid value for p') 
end 
if r<0 
   error('invalid value for r') 
end 
X=r+10; 
while cmb(X-1, r-1)*(p^r)*((1-p)^(X-r)) > 1e-6 
   X=X+10; 
end 
x=[r:X]; 
n=ones(1, length(x))*r; 
P=cmb(x-1, r-1).*(p.^r).*((1-p).^(x-r)); 
pmf=[1 1; x' P'];