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rig

Generate inverse Gaussian random deviates


Description

Generates inverse Gaussian random deviates.

Usage

rig(n,mean,scale)

Arguments

n

the number of deviates required. If this has length > 1 then the length is taken as the number of deviates required.

mean

vector of mean values.

scale

vector of scale parameter values (lambda, see below)

Details

If x if the returned vector, then E(x) = mean while var(x) = scale*mean^3. For density and distribution functions see the statmod package. The algorithm used is Algorithm 5.7 of Gentle (2003), based on Michael et al. (1976). Note that scale here is the scale parameter in the GLM sense, which is the reciprocal of the usual ‘lambda’ parameter.

Value

A vector of inverse Gaussian random deviates.

Author(s)

Simon N. Wood simon.wood@r-project.org

References

Gentle, J.E. (2003) Random Number Generation and Monte Carlo Methods (2nd ed.) Springer.

Michael, J.R., W.R. Schucany & R.W. Hass (1976) Generating random variates using transformations with multiple roots. The American Statistician 30, 88-90.

Examples

require(mgcv)
set.seed(7)
## An inverse.gaussian GAM example, by modify `gamSim' output... 
dat <- gamSim(1,n=400,dist="normal",scale=1)
dat$f <- dat$f/4 ## true linear predictor 
Ey <- exp(dat$f);scale <- .5 ## mean and GLM scale parameter
## simulate inverse Gaussian response...
dat$y <- rig(Ey,mean=Ey,scale=.2)
big <- gam(y~ s(x0)+ s(x1)+s(x2)+s(x3),family=inverse.gaussian(link=log),
          data=dat,method="REML")
plot(big,pages=1)
gam.check(big)
summary(big)

mgcv

Mixed GAM Computation Vehicle with Automatic Smoothness Estimation

v1.8-35
GPL (>= 2)
Authors
Simon Wood <simon.wood@r-project.org>
Initial release

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