[R] calculating std err (SEM)?

[JRG]

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
> kill. 
> 

Would that perhaps be  sd(x,na.rm=TRUE)/sqrt(sum(!is.na(x))) ?

---JRG


John R. Gleason

Syracuse University
430 Huntington Hall                      Voice:   315-443-3107
Syracuse, NY 13244-2340  USA             FAX:     315-443-4085

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