pgfDpoisson {Compounding} R Documentation

## Function pgfDpoisson.

### Description

This function calculates value of the pgf's first derivative of the Poisson distribution.

### Usage

```pgfDpoisson(s, params)
```

### Arguments

 `s` Value of the parameter of the pgf. It should be form interval [-1,1]. In the opposite pgf diverges. `params` Positive parameter of the Poisson distribution, such that params<-theta.

### Author(s)

S. Nadarajah, B. V. Popovic, M. M. Ristic

### References

Johnson N, Kotz S, Kemp A (1992) Univariate Discrete Distributions, John Wiley and Sons, New York

http://www.am.qub.ac.uk/users/g.gribakin/sor/Chap3.pdf

### Examples

```params<-7
pgfDpoisson(.5,params)

## The function is currently defined as

pgfDpoisson <- function(s,params) {
k<-s[abs(s)>1]
if (length(k)>0)
warning("At least one element of the vector s are out of interval [-1,1]")
if (length(params)>1) stop("The length of params is 1")
theta<-params
if (theta<=0)
stop ("Parameter of Poisson distribution must be positive")
theta*exp(theta*(s-1))
}
```

[Package Compounding version 1.0.2 Index]