CumulantGeneratingFunction
CumulantGeneratingFunction[dist,t]
gives the cumulant-generating function for the distribution dist as a function of the variable t.
CumulantGeneratingFunction[dist,{t1,t2,…}]
gives the cumulant-generating function for the multivariate distribution dist as a function of the variables t1, t2, … .
Details
- CumulantGeneratingFunction[dist,t] is given by Log[MomentGeneratingFunction[dist,t]].
- CumulantGeneratingFunction[dist, {t1,t2,…}] is given by Log[MomentGeneratingFunction[dist,{t1,t2,…}]].
- The i cumulant can be extracted from a cumulant-generating function cgf through SeriesCoefficient[cgf,{t,0,i}]i!.
Examples
open allclose allBasic Examples (3)
Scope (5)
Applications (5)
The cumulant-generating function of a difference of two independent random variables is equal to the sum of their cumulant-generating functions with oppositive sign arguments:
Illustrate the central limit theorem:
Find the cumulant-generating function for the standardized random variate:
Find the moment-generating function for the sum of standardized random variates rescaled by :
Compare with the moment-generating function of a standard normal distribution:
Find the Esscher premium for insuring against losses following GammaDistribution:
Construct a Bernstein–Chernoff bound for the survival function :
Large approximation of the bound:
Construct Daniel's saddle point approximation to PDF of VarianceGammaDistribution:
Find the saddle point associated with the argument of probability density function :
Select the solution that is valid for all real , including the origin:
The approximation is constructed using the cumulant-generating function at the saddle point:
Properties & Relations (3)
Exponential of CumulantGeneratingFunction gives MomentGeneratingFunction:
CumulantGeneratingFunction is an exponential generating function for the sequence of cumulants:
Use CumulantGeneratingFunction directly:
Use SeriesCoefficient formulation:
Possible Issues (2)
For some distributions with long tails, cumulants of only several low orders are defined:
Correspondingly, CumulantGeneratingFunction is undefined:
CumulantGeneratingFunction is not always known in closed form:
Use Cumulant to find cumulants directly:
Text
Wolfram Research (2010), CumulantGeneratingFunction, Wolfram Language function, https://reference.wolfram.com/language/ref/CumulantGeneratingFunction.html.
CMS
Wolfram Language. 2010. "CumulantGeneratingFunction." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/CumulantGeneratingFunction.html.
APA
Wolfram Language. (2010). CumulantGeneratingFunction. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/CumulantGeneratingFunction.html