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

-----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