> # Gamma in R
> rgamma(5,shape=4,scale=2)
[1] 4.941189 6.153463 4.307587 4.610195 6.857368
> a<-rgamma(1000,4,2)
> mean(a)
[1] 1.984818
> mean(rgamma(1000,4,1/2))
[1] 7.772662
> var(rgamma(1000,4,1/2))
[1] 16.56176
> mean(rgamma(1000,4,1/4))
[1] 16.37157
> var(rgamma(1000,4,1/4))
[1] 65.32456
> # CDF of gamma
> pgamma(20,4,1/4)
[1] 0.7349741
> # 90th percentile
> qgamma(.90,4,1/4)
[1] 26.72313

> # Chi-square
> rchisq(5, df=7)
[1] 5.671996 6.088484 2.196321 2.324622 9.104103
> mean(rchisq(1000, df=7))
[1] 6.992071
> var(rchisq(1000, df=7))
[1] 13.10064
> pchisq(10.0,7)
[1] 0.8114265
> # 90th percentile
> qchisq(.90,7)
[1] 12.01704

> # Normal
> rnorm(5,mean=10,sd=4)
[1] 11.898977  8.509594 14.206274  8.069501 12.699667
> mean(rnorm(1000,mean=10,sd=4))
[1] 10.09516
> var(rnorm(1000,mean=10,sd=4))
[1] 15.26775
> # CDF of normal
> pnorm(15.0,10,4)
[1] 0.8943502
> # 90th percentile
> qnorm(.90,10,4)
[1] 15.12621