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Wolfram Language & System Documentation Center
FactorialMomentGeneratingFunction
  • See Also
    • FactorialMoment
    • Expectation
    • CharacteristicFunction
    • MomentGeneratingFunction
    • CentralMomentGeneratingFunction
    • CumulantGeneratingFunction
    • GeneratingFunction
  • Related Guides
    • Statistical Moments and Generating Functions
    • Statistical Distribution Functions
    • See Also
      • FactorialMoment
      • Expectation
      • CharacteristicFunction
      • MomentGeneratingFunction
      • CentralMomentGeneratingFunction
      • CumulantGeneratingFunction
      • GeneratingFunction
    • Related Guides
      • Statistical Moments and Generating Functions
      • Statistical Distribution Functions

FactorialMomentGeneratingFunction[dist,t]

gives the factorial moment-generating function for the distribution dist as a function of the variable t.

FactorialMomentGeneratingFunction[dist,{t1,t2,…}]

gives the factorial moment-generating function for the multivariate distribution dist as a function of the variables t1, t2, ….

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Applications  
Properties & Relations  
Possible Issues  
See Also
Related Guides
History
Cite this Page
BUILT-IN SYMBOL
  • See Also
    • FactorialMoment
    • Expectation
    • CharacteristicFunction
    • MomentGeneratingFunction
    • CentralMomentGeneratingFunction
    • CumulantGeneratingFunction
    • GeneratingFunction
  • Related Guides
    • Statistical Moments and Generating Functions
    • Statistical Distribution Functions
    • See Also
      • FactorialMoment
      • Expectation
      • CharacteristicFunction
      • MomentGeneratingFunction
      • CentralMomentGeneratingFunction
      • CumulantGeneratingFunction
      • GeneratingFunction
    • Related Guides
      • Statistical Moments and Generating Functions
      • Statistical Distribution Functions

FactorialMomentGeneratingFunction

FactorialMomentGeneratingFunction[dist,t]

gives the factorial moment-generating function for the distribution dist as a function of the variable t.

FactorialMomentGeneratingFunction[dist,{t1,t2,…}]

gives the factorial moment-generating function for the multivariate distribution dist as a function of the variables t1, t2, ….

Details

  • FactorialMomentGeneratingFunction is also known as probability generating function (pgf).
  • FactorialMomentGeneratingFunction[dist,t] is equivalent to Expectation[tx,xdist].
  • FactorialMomentGeneratingFunction[dist, {t1,t2,…}] is equivalent to Expectation[t1x1t2x2…,{x1,x2,…}dist].
  • The i^(th) factorial moment can be extracted from a factorial moment-generating function fmgf through SeriesCoefficient[fmgf,{t,1,i}]i!.
  • The probability for a discrete random variable to assume the value i can be extracted from a factorial moment-generating function expr through SeriesCoefficient[expr,{t,0,i}].

Examples

open all close all

Basic Examples  (3)

The factorial moment-generating function (fmgf) for a univariate discrete distribution:

Compute an fmgf for a continuous univariate distribution:

The fmgf for a multivariate distribution:

Scope  (5)

Find the factorial moment-generating function (fmgf) for a discrete formula distribution:

Compute the fmgf for data distribution:

Find the fmgf for a censored distribution:

Compute the fmgf for parameter mixture distribution:

Find the fmgf for the slice distribution of a random process:

Applications  (6)

Find the fmgf for the sum of i.i.d. geometric variates:

Compare with the fmgf of NegativeBinomialDistribution:

Find the fmgf of the sum of a random number of i.i.d. geometric random variates, assuming follows PoissonDistribution:

Compare with the fmgf of PolyaAeppliDistribution:

Find the PDF of a non-negative integer random variate from its fmgf:

Use the probability generating function interpretation:

Show the probability mass function:

Verify normalization:

Construct a probability generating function for BernoulliDistribution:

Construct its Lagrange transformation, and use it as a new probability generating function:

Compare it with the probability generating function of a shifted GeometricDistribution:

Apply a Lagrange transformation to the probability generating function (pgf) of GeometricDistribution:

Reconstruct PDF:

The resulting distribution is known as Haight's distribution. It is only normalized to 1 for :

Show the probability mass function:

Find the distribution of the number of times a biased coin should be flipped until heads appear twice in a row. Let be the probability of heads. Event space is comprised of three types of events: tail (T), head then tail (HT), and two heads in a row (HH) with probabilities:

Find the fmgf of the random variate of interest, interpreting it as the total of the number of T events added to double the number of HT events plus 2:

Reconstruct PDF:

Compute mean:

Find variance using relation:

Properties & Relations  (3)

FactorialMomentGeneratingFunction is equivalent to Expectation of :

For non-negative discrete variates, the fmgf is the probability generating function (pgf):

The factorial moments can be extracted from the factorial moment-generating function:

Alternatively, use SeriesCoefficient:

Possible Issues  (2)

For some distributions with long tails, factorial moments of only several low orders are defined:

Correspondingly, the factorial moment-generating function is not defined:

FactorialMomentGeneratingFunction is not always known in closed form:

See Also

FactorialMoment  Expectation  CharacteristicFunction  MomentGeneratingFunction  CentralMomentGeneratingFunction  CumulantGeneratingFunction  GeneratingFunction

Related Guides

    ▪
  • Statistical Moments and Generating Functions
  • ▪
  • Statistical Distribution Functions

History

Introduced in 2010 (8.0)

Wolfram Research (2010), FactorialMomentGeneratingFunction, Wolfram Language function, https://reference.wolfram.com/language/ref/FactorialMomentGeneratingFunction.html.

Text

Wolfram Research (2010), FactorialMomentGeneratingFunction, Wolfram Language function, https://reference.wolfram.com/language/ref/FactorialMomentGeneratingFunction.html.

CMS

Wolfram Language. 2010. "FactorialMomentGeneratingFunction." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/FactorialMomentGeneratingFunction.html.

APA

Wolfram Language. (2010). FactorialMomentGeneratingFunction. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/FactorialMomentGeneratingFunction.html

BibTeX

@misc{reference.wolfram_2025_factorialmomentgeneratingfunction, author="Wolfram Research", title="{FactorialMomentGeneratingFunction}", year="2010", howpublished="\url{https://reference.wolfram.com/language/ref/FactorialMomentGeneratingFunction.html}", note=[Accessed: 01-May-2026]}

BibLaTeX

@online{reference.wolfram_2025_factorialmomentgeneratingfunction, organization={Wolfram Research}, title={FactorialMomentGeneratingFunction}, year={2010}, url={https://reference.wolfram.com/language/ref/FactorialMomentGeneratingFunction.html}, note=[Accessed: 01-May-2026]}

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