//-------------------------------------------------------------------
//	geodist.cpp
//
//	This program displays a probability distribution and graph
//	for the Geometric Distribution based on the parameter  p .
//
//		to compile:  $ g++ geodist.cpp -o geodist
//		to execute:  $ ./geodist
//
//	programmer: ALLAN CRUSE
//	written on: 22 FEB 2011
//-------------------------------------------------------------------

#include <stdio.h>	// for printf()  
#include <math.h>	// for sqrt() 

#define N_MAX	50

double	p = 0.08;	
double	mu, sigma, q;

double freq( unsigned int k )
{
	// returns the value of the geometric distribution at k
	// (namely, q^(k-1) * p )
	if ( k == 0 ) return 0.0;
	double	retval = p;
	for (int i = 1; i < k; i++) retval *= q;
	return	retval;	
}

int main( int argc, char **argv )
{
	// initialize global variables
	int	n = N_MAX;
	q = 1.0 - p;
	mu = 1.0 / p;
	sigma = sqrt( q / (p * p) );

	// exhibit the geometric distribution function
	printf( "\n" );
	printf( " Geometric probability distribution" );
	printf( " for n=%d and p=%1.5f \n\n", n, p );
	for (int k = 0; k <= n; k++)
		{
		double	prob = freq( (double)k );
		printf( " k=%-3d ", k );
		printf( "prob=%1.5f ", prob );
		int	m = (int)( 300.0 * prob );
		for (int j = 0; j < m; j++) printf( "*" );
		printf( "\n" );
		}

	// report this distribution's statistical parameters
	printf( "\n n=%d  mu=%1.5f  sigma=%1.5f \n\n", n, mu, sigma );
}