Hi:
I am working on a relatively simple project. I am attempting to generate a
Poisson distribution for the number of ambulances that are dispatched. I have
looked at my database and determined the average number of ambulances
dispatched is 9
How do I get a Poisson distribution to be generated using the Commons Math?
The output I am expecting to generate looks like this....
Likelihood of 1 ambulance dispatched is 0.005
Likelihood of 2 ambulances dispatched is 0.015
Likelihood of 3 ambulances dispatched is 0.034
Likelihood of 4 ambulances dispatched is 0.61
Likelihood of 5 ambulances dispatched is 0.091
Likelihood of 6 ambulances dispatched is 0.117
Etc.
This is probably a very simple programming question for many of you. But for me
as a novice it is not easy.
So far, here is what I have using Commons Math;
import org.apache.commons.math3.distribution.PoissonDistribution;
public class poissonDistribution
{
public static void main(String[] args)
{
PoissonDistribution ambulanceDistribution = new
PoissonDistribution(9);
System.out.println(ambulanceDistribution);
}
}
The console output is;
"org.apache.commons.math3.distribution.PoissonDistribution@27716f4"
I did try and take matters into my own hands and write the equation out (shown
below). But I have a very strong preference to use a method provided by Commons
Math. I am much more confident in Commons Math than my own abilities.
The following is my code. It works in a fashion, but I am not confident in it.
Shown below is what I am currently using - but prefer to avoid using this;
import java.lang.Math;
public class PoissonExperiment1
{
public static void main(String[] args)
{
// c is the average number of calls per hour. This is a variable
that is
// derived from your database.
double c = 9.0;
// k is the number of expected calls we want to determine the
probability
int k = 1;
while (k <= 20)
{
int factorialResult = 1;
for (int i = 1; i <= k; i++)
{
factorialResult = factorialResult * i;
}
double term1 = (Math.pow(Math.E, -c));
double term2 = Math.pow(c, k);
double numerator = term1 * term2;
double answer = numerator / factorialResult;
System.out.format("%10.3f:%n ", answer);
k++;
}
}
}
Thank you for your consideration and time,
David
David Kulpanowski
Database Analyst
Lee County Public Safety
PO Box 398
Fort Myers, FL 33902
[email protected]
239-533-3962
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