[R] calculating std err (SEM)?
loesljrg at accucom.net
Fri Mar 1 18:18:24 CET 2002
On 1 Mar 02, at 16:44, Peter Dalgaard BSA wrote:
> "Kirk R. Wythers" <kwythers at umn.edu> writes:
> > Is there a "canned" function in R for finding the standard error of the
> > mean? I have tried
> > > sem <- function(x) c(mean =mean(x),
> > + SEM = stdev(x)/sqrt(length(x)))
> > > sem(pnet.lai)
> > Error in sem(pnet.lai) : couldn't find function "stdev"
> > It looks like there is no stdev function in R
> It's sd() (as help.search("deviation") might have told you). Also,
> beware of missing values: sd(x,na.rm=TRUE)/sum(!is.na(x)) is the sure
Would that perhaps be sd(x,na.rm=TRUE)/sqrt(sum(!is.na(x))) ?
John R. Gleason
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