[R] What's going on? (strange standard deviation)

[Deepayan Sarkar]

On Friday 15 November 2002 03:18 pm, Matej Cepl wrote:
> I have probably misunderstood something (again :-():
> 	> CEMPLOY<-TEMPLOY[!is.na(TEMPLOY)]
> 	> sum(CEMPLOY^2/length(CEMPLOY))-mean(CEMPLOY)^2
>
> 	[1] 30877.28
>
> 	> var(TEMPLOY,na.rm=TRUE)
>
> 	[1] 30981.25
>
> Could anybody tell me, what's going on? I suppose that
>
> 	var=sum(x^2/N)-xbar^2
>
> or what did I enter wrong?


Is length(CEMPLOY) approximately 300 ?

?var says:

Details:

     [...]

     The denominator n - 1 is used which gives an unbiased estimator of
     the (co)variance for i.i.d. observations. These functions return
     `NA' when there is only one observation (whereas S-plus has been
     returning `NaN'), and from R 1.2.3 fail if `x' has length zero.


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