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From Ole Ersoy <ole.er...@gmail.com>
Subject Re: [math] Poisson distribution to show how many ambulances are dispatched per hour
Date Mon, 31 Aug 2015 16:41:36 GMT
Hi David,

public static void main(String[] args)
{
         int numberOfAmbulances = 20;
         PoissonDistribution ambulanceDistribution = new PoissonDistribution(9);

         for (int dispatched = 0; dispatched <= numberOfAmbulances; dispatched++) {
             System.out.println("Likelihood of " + dispatched + " ambulances dispatched is
" + ambulanceDistribution.probability(dispatched) + "\n");
         }
}

Cheers,
- Ole

On 08/31/2015 11:21 AM, Kulpanowski, David wrote:
> 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
> DKulpanowski@Leegov.com
> 239-533-3962
>
>
>
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