Using R to illustrate the Central Limit Theorem
"Kevin E. Thorpe" <kevin.thorpe at utoronto.ca> writes:
rparab <- function(nn) {
u <- 2*runif(nn) - 1
ifelse(u<0,-(abs(u)^(1/3)),u^(1/3))
}
It seems that in my version of R (2.0.1) on Linux, that calculating the cube
root of a negative number using ^(1/3) returns NaN. I looked at the help in
the arithmetic operators and did help.search("cube root"),
help.search("root")
and help.search("cube") and recognised no alternatives. So I used an
ifelse() to
deal with the negatives. Have I missed something really elementary?
Not really. You might have used u <- runif(nn,-1,1) and sign(u)*abs(u)^(1/3) instead of the ifelse construct (remember that ifelse generally evaluates both the 'yes' and 'no' parts and on some architectures the NaN results may be slow to compute).
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907