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java.lang.Objectcern.colt.PersistentObject
cern.jet.random.AbstractDistribution
cern.jet.random.AbstractDiscreteDistribution
cern.jet.random.PoissonSlow
public class PoissonSlow
Poisson distribution; See the math definition and animated definition.
p(k) = (mean^k / k!) * exp(-mean) for k >= 0.
Valid parameter ranges: mean > 0. Note: if mean <= 0.0 then always returns zero.
Instance methods operate on a user supplied uniform random number generator; they are unsynchronized.
Implementation: This is a port of RandPoisson used in CLHEP 1.4.0 (C++). CLHEP's implementation, in turn, is based upon "W.H.Press et al., Numerical Recipes in C, Second Edition".
Field Summary | |
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protected double |
cached_alxm
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protected double |
cached_g
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protected double |
cached_sq
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protected static double[] |
cof
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protected double |
mean
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protected static double |
MEAN_MAX
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protected static PoissonSlow |
shared
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protected static double |
SWITCH_MEAN
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Fields inherited from class cern.jet.random.AbstractDistribution |
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randomGenerator |
Fields inherited from class cern.colt.PersistentObject |
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serialVersionUID |
Constructor Summary | |
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PoissonSlow(double mean,
RandomEngine randomGenerator)
Constructs a poisson distribution. |
Method Summary | |
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static double |
logGamma(double xx)
Returns the value ln(Gamma(xx) for xx > 0. |
int |
nextInt()
Returns a random number from the distribution. |
protected int |
nextIntSlow()
Returns a random number from the distribution. |
void |
setMean(double mean)
Sets the mean. |
static int |
staticNextInt(double mean)
Returns a random number from the distribution with the given mean. |
String |
toString()
Returns a String representation of the receiver. |
Methods inherited from class cern.jet.random.AbstractDiscreteDistribution |
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nextDouble |
Methods inherited from class cern.jet.random.AbstractDistribution |
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apply, apply, clone, getRandomGenerator, makeDefaultGenerator, setRandomGenerator |
Methods inherited from class java.lang.Object |
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equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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protected double mean
protected double cached_sq
protected double cached_alxm
protected double cached_g
protected static final double MEAN_MAX
protected static final double SWITCH_MEAN
protected static final double[] cof
protected static PoissonSlow shared
Constructor Detail |
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public PoissonSlow(double mean, RandomEngine randomGenerator)
Method Detail |
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public static double logGamma(double xx)
public int nextInt()
nextInt
in class AbstractDiscreteDistribution
protected int nextIntSlow()
public void setMean(double mean)
public static int staticNextInt(double mean)
public String toString()
toString
in class Object
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