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cdfpoi(1) Scilab Function cdfpoi(1)
NAME
cdfpoi - cumulative distribution function poisson distribution
CALLING SEQUENCE
[P,Q]=cdfpoi("PQ",S,Xlam)
[S]=cdfpoi("S",Xlam,P,Q)
[Xlam]=cdfpoi("Xlam",P,Q,S);
PARAMETERS
P,Q,S,Xlam
: four real vectors of the same size.
P,Q (Q=1-P)
: The cumulation from 0 to S of the poisson density. Input
range: [0,1].
S :Upper limit of cumulation of the Poisson. Input range: [0,
+infinity). Search range: [0,1E300]
Xlam : Mean of the Poisson distribution. Input range: [0, +infin-
ity). Search range: [0,1E300]
DESCRIPTION
Calculates any one parameter of the Poisson distribution given values for
the others.
Formula 26.4.21 of Abramowitz and Stegun, Handbook of Mathemati-
cal Functions (1966) is used to reduce the computation of the cumulative
distribution function to that of computing a chi-square, hence an incom-
plete gamma function.
Cumulative distribution function (P) is calculated directly. Computa-
tion of other parameters involve a seach for a value that produces the
desired value of P. The search relies on the monotinicity of P with
the other parameter.
From DCDFLIB: Library of Fortran Routines for Cumulative Distribution Func-
tions, Inverses, and Other Parameters (February, 1994) Barry W. Brown,
James Lovato and Kathy Russell. The University of Texas.
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