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java.lang.Objectorg.apache.commons.math.distribution.AbstractDistribution
org.apache.commons.math.distribution.AbstractIntegerDistribution
org.apache.commons.math.distribution.PoissonDistributionImpl
public class PoissonDistributionImpl
Implementation for the PoissonDistribution
.
Constructor Summary | |
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PoissonDistributionImpl(double p)
Create a new Poisson distribution with the given the mean. |
Method Summary | |
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double |
cumulativeProbability(int x)
The probability distribution function P(X <= x) for a Poisson distribution. |
double |
getMean()
Get the Poisson mean for the distribution. |
double |
normalApproximateProbability(int x)
Calculates the Poisson distribution function using a normal approximation. |
double |
probability(int x)
The probability mass function P(X = x) for a Poisson distribution. |
void |
setMean(double p)
Set the Poisson mean for the distribution. |
Methods inherited from class org.apache.commons.math.distribution.AbstractIntegerDistribution |
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cumulativeProbability, cumulativeProbability, inverseCumulativeProbability, probability |
Methods inherited from class org.apache.commons.math.distribution.AbstractDistribution |
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cumulativeProbability |
Methods inherited from class java.lang.Object |
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equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface org.apache.commons.math.distribution.IntegerDistribution |
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cumulativeProbability, inverseCumulativeProbability |
Methods inherited from interface org.apache.commons.math.distribution.DiscreteDistribution |
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probability |
Methods inherited from interface org.apache.commons.math.distribution.Distribution |
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cumulativeProbability, cumulativeProbability |
Constructor Detail |
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public PoissonDistributionImpl(double p)
IllegalArgument
is thrown.
p
- the Poisson mean
java.lang.IllegalArgumentException
- if p ≤ 0Method Detail |
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public double getMean()
getMean
in interface PoissonDistribution
public void setMean(double p)
IllegalArgument
is thrown.
setMean
in interface PoissonDistribution
p
- the Poisson mean value
java.lang.IllegalArgumentException
- if p ≤ 0public double probability(int x)
probability
in interface IntegerDistribution
x
- the value at which the probability density function is evaluated.
public double cumulativeProbability(int x) throws MathException
cumulativeProbability
in interface IntegerDistribution
cumulativeProbability
in class AbstractIntegerDistribution
x
- the value at which the PDF is evaluated.
MathException
- if the cumulative probability can not be
computed due to convergence or other numerical errors.public double normalApproximateProbability(int x) throws MathException
N(mean, sqrt(mean))
distribution is used to approximate the Poisson distribution.
The computation uses "half-correction" -- evaluating the normal
distribution function at x + 0.5
normalApproximateProbability
in interface PoissonDistribution
x
- the upper bound, inclusive
MathException
- if an error occurs computing the normal approximation
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