[R] Still a bug with NA in sd() or var()?

[Austin, Matt]

The behavior is actually documented in the var() help file (?var), although
it's not clear that this would be the behavior if you just read ?sd.  sd()
does call var if you look at the code, so the behavior should not be
unexpected.

--Matt

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Roger Dungan
> Sent: Monday, October 31, 2005 1:24 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Still a bug with NA in sd() or var()?
> 
> 
> Dear R-users,
> 
> Running R 2.1.1 in WindowsXP, there seems to be a 'bug' in sd()
> If
> >x<-c(1,2,3,NA,5)
> >mean(x) 
> [1] NA
> 
> But 
> >sd(x) 
> Or
> >var(x)
> give
> Error in var(x, na.rm = na.rm) : missing observations in cov/cor
> 
> There are obvious work-rounds, like
> >sd(x, is.na(x)==F)
> which gives the result (with error message)
> [1] 1.707825
> Warning message:
> the condition has length > 1 and only the first element will 
> be used in:
> if (na.rm) "complete.obs" else "all.obs"
> 
> or
> 
> >y<-subset(x, is.na(x)==F)
> >sd(y)
> [1] 1.707825
> 
> Am I missing something, or is this a problem with sd()? Why 
> does mean(x)
> give a simple NA, but var(x) requires some additional work? There was
> some previous discussion in r-help about this for R v 1.6.0, with
> mention of a fix for 1.6.1. 
> 
> Dr Roger Dungan
> School of Biological Sciences
> University of Cantebury
> Christchurch, New Zealand
> ph +64 3 366 7001 ext. 4848
> fax +64 3 364 2590
> 
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