% drv.m - plot discrete random variable pmfs
% 

clear all
clf
echo off

% Bernoulli(q)
q=0.7;
x=[0 1];
p=[0.3 0.7];
figure(1)
subplot(221),stem(x,p);
axis([-1 2 0 1])
title('Bernoulli(0.7) pmf')
clear q,x,p

% geometric_0(p)
p=0.7;
k=[0:9];
pk=(1-p)*p.^k;
subplot(222),stem(k,pk)
%axis([k(1) k(length(k)) 0 1])
title('Geometric_0(0.7) pmf')
clear p,k,pk

% Poisson(lambda)
lambda=5;
k=[0:14]; lk=length(k);
pk(1)=exp(-lambda);
for i=2:lk,
   pk(i)=pk(i-1)*lambda/i;
end
subplot(223),stem(k,pk)
%axis([k(1) k(lk) 0 1])
title('Poisson(5) pmf')
clear lambda,k,lk,pk

% binomial(n,p)
n=10; k=[0:n];
p=0.3;
pk=factorial(n)*(1-p)^n*(p/(1-p)).^k;
pk(1)=pk(1)/factorial(n);
pk(n+1)=pk(n+1)/factorial(n);
for i=2:n,
   pk(i)=pk(i)/(factorial(i)*factorial(n-i));
end
subplot(224),stem(k,pk)
title('binomial(10,0.3) pmf')