On Sep 2, 2014, at 6:52 PM, Lucy Leigh wrote: > Hi, > I wish to simulate some data from a Weibull distribution. The rweibull > function in R uses the parameterisation > > 'with shape parameter a and scale parameter b has density given by f(x) = > (a/b) (x/b)^(a-1) exp(- (x/b)^a)'. > > However, it would be much more useful for me to simulate data using a > different parameterisation of the > > Weibull, with shape a1 and scale b1, namely f(x) = > a1*b1*x^(a1-1)exp(-b1*x^a1). > > However I'm not sure how to do this, as I have only ever used the random > generators that come pre-programmed in R. > > Is there a package or example someone can point me to that demonstrates how > to simulate data from any given distribution?
You could look at an alternative parametrization in pkg:survival. An exmaple in the survreg docs says: # Weibull parametrisation y<-rweibull(1000, shape=2, scale=5) survreg(Surv(y)~1, dist="weibull") # survreg scale parameter maps to 1/shape, linear predictor to log(scale) David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
