R help - Mar 2002 - calculating std err (SEM)?

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

Thanks,

Kirk



Kirk R. Wythers				email: kwythers at umn.edu
University of Minnesota			tel: 612.625.2261
Department of Forest Resources		fax: 612.625.5212
Saint Paul, MN 55108
					

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"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. 

-- 
   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
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try sd(x)

ap

----------------------------------------------------------------------
Andrew J Perrin - andrew_perrin at unc.edu - http://www.unc.edu/~aperrin
 Assistant Professor of Sociology, U of North Carolina, Chapel Hill
      269 Hamilton Hall, CB#3210, Chapel Hill, NC 27599-3210 USA


On 1 Mar 2002, Kirk R. Wythers wrote:
> 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
> 
> Thanks,
> 
> Kirk
> 
> 
> 
> Kirk R. Wythers				email: kwythers at umn.edu
> University of Minnesota			tel: 612.625.2261
> Department of Forest Resources		fax: 612.625.5212
> Saint Paul, MN 55108
> 					
> 
>
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> r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at
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>
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> 
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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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