| java.lang.Object
 org.apache.commons.math.distribution.AbstractDistribution
org.apache.commons.math.distribution.AbstractIntegerDistribution
org.apache.commons.math.distribution.PoissonDistributionImpl
| Constructor Summary | |
| public | PoissonDistributionImpl(double p)
Create a new Poisson distribution with the given the mean. |
| Method Summary | |
| public double | cumulativeProbability(int x)
The probability distribution function P(X <= x) for a Poisson distribution.
Parameters:
x - the value at which the PDF is evaluated. | | protected int | getDomainLowerBound(double p)
Access the domain value lower bound, based on p, used to
bracket a CDF root. | | protected int | getDomainUpperBound(double p)
Access the domain value upper bound, based on p, used to
bracket a CDF root. | | public double | getMean()
Get the Poisson mean for the distribution. | | public double | normalApproximateProbability(int x)
Calculates the Poisson distribution function using a normal
approximation. | | public double | probability(int x)
The probability mass function P(X = x) for a Poisson distribution.
Parameters:
x - the value at which the probability density function is evaluated. | | public void | setMean(double p)
Set the Poisson mean for the distribution. |
| PoissonDistributionImpl | | public PoissonDistributionImpl(double p)(Code) | | Create a new Poisson distribution with the given the mean.
The mean value must be positive; otherwise an
IllegalArgument is thrown.
Parameters:
p - the Poisson mean
throws:
IllegalArgumentException - if p ≤ 0 |
| cumulativeProbability | | public double cumulativeProbability(int x) throws MathException(Code) | | The probability distribution function P(X <= x) for a Poisson distribution.
Parameters:
x - the value at which the PDF is evaluated. Poisson distribution function evaluated at x
throws:
MathException - if the cumulative probability can not becomputed due to convergence or other numerical errors. |
| getDomainLowerBound | | protected int getDomainLowerBound(double p)(Code) | | Access the domain value lower bound, based on p, used to
bracket a CDF root. This method is used by
PoissonDistributionImpl.inverseCumulativeProbability(double) to find critical values.
Parameters:
p - the desired probability for the critical value domain lower bound |
| getDomainUpperBound | | protected int getDomainUpperBound(double p)(Code) | | Access the domain value upper bound, based on p, used to
bracket a CDF root. This method is used by
PoissonDistributionImpl.inverseCumulativeProbability(double) to find critical values.
Parameters:
p - the desired probability for the critical value domain upper bound |
| getMean | | public double getMean()(Code) | | Get the Poisson mean for the distribution.
the Poisson mean for the distribution. |
| normalApproximateProbability | | public double normalApproximateProbability(int x) throws MathException(Code) | | Calculates the Poisson distribution function using a normal
approximation. The 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
Parameters:
x - the upper bound, inclusive the distribution function value calculated using a normal approximation
throws:
MathException - if an error occurs computing the normal approximation |
| probability | | public double probability(int x)(Code) | | The probability mass function P(X = x) for a Poisson distribution.
Parameters:
x - the value at which the probability density function is evaluated. the value of the probability mass function at x |
| setMean | | public void setMean(double p)(Code) | | Set the Poisson mean for the distribution.
The mean value must be positive; otherwise an
IllegalArgument is thrown.
Parameters:
p - the Poisson mean value
throws:
IllegalArgumentException - if p ≤ 0 |
| Methods inherited from org.apache.commons.math.distribution.AbstractDistribution | public double cumulativeProbability(double x0, double x1) throws MathException(Code)(Java Doc)
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