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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) ENPC
// Copyright (C) ????-2008 - INRIA
// Copyright (C) 2010 - DIGITEO - Allan CORNET
//
// This file is released under the 3-clause BSD license. See COPYING-BSD.
function [z]=PoissonT(n)
function [y]=Poisson(m,n,pmean)
// P{n} = exp(-lambda)lambda^n/n!
// pmean =lambda
//----------------------------
y=0*ones(m,n)
bound= exp(-pmean);
for i=1:m*n,
count = 0;
lprod = 1;
while( lprod >= bound), lprod = lprod*rand(1,1,"uniform");
count = count + 1;
end
y(i) = count - 1;
end
y = matrix(y, m, n);
endfunction
[lhs, rhs] = argn(0);
if rhs <= 0 ; n = 1000;end
pmean = 3;
y = Poisson(1, n, pmean);
N = 20;
i = 0:N;
z = [];
for i1=i, z=[z,prod(size(find(y==i1)))],end
drawlater();
my_handle = scf(100001);
clf(my_handle, "reset");
demo_viewCode("poisson.dem.sce");
plot2d3("onn",i',z'/n,1);
deff("[y]=fact(n)","if n==0 then y=1;else y=n*fact(n-1);end");
zt=[];for i1=0:N; zt=[zt, exp(-pmean) *pmean^i1/fact(i1)];end
plot2d1("onn",i',zt',[-2,6]);
xtitle(_("Simulation of a Poisson random variable"));
current_axe = gca();
current_axe.title.font_size = 3;
current_axe.background = color(232,230,200);
legend([_("Simulation");_("Theory")]);
drawnow();
endfunction
PoissonT();
clear PoissonT;
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