Generate Tweedie random deviates
Generates Tweedie random deviates, for powers between 1 and 2.
rTweedie(mu,p=1.5,phi=1)
mu |
vector of expected values for the deviates to be generated. One deviate generated for each element of |
p |
the variance of a deviate is proportional to its mean, |
phi |
The scale parameter. Variance of the deviates is given by is |
A Tweedie random variable with 1<p<2 is a sum of N
gamma random variables
where N
has a Poisson distribution, with mean mu^(2-p)/((2-p)*phi)
. The Gamma random variables
that are summed have shape parameter (2-p)/(p-1)
and scale parameter phi*(p-1)*mu^(p-1)
(note that
this scale parameter is different from the scale parameter for a GLM with Gamma errors).
This is a restricted, but faster, version of rtweedie
from the tweedie
package.
A vector of random deviates from a Tweedie distribution, expected value vector mu
, variance vector phi*mu^p
.
Simon N. Wood simon.wood@r-project.org
Peter K Dunn (2009). tweedie: Tweedie exponential family models. R package version 2.0.2. https://cran.r-project.org/package=tweedie
library(mgcv) f2 <- function(x) 0.2 * x^11 * (10 * (1 - x))^6 + 10 * (10 * x)^3 * (1 - x)^10 n <- 300 x <- runif(n) mu <- exp(f2(x)/3+.1);x <- x*10 - 4 y <- rTweedie(mu,p=1.5,phi=1.3) b <- gam(y~s(x,k=20),family=Tweedie(p=1.5)) b plot(b)
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