[R] Mean of difftime vectors : "code infelicity" or intended behaviour ?
charpent at bacbuc.dyndns.org
Tue Mar 17 08:04:22 CET 2009
Oops. Clicked "Send" too fast (don't shoot, Brian !). I forgot :
R version 2.8.1 (2008-12-22)
attached base packages:
 stats graphics grDevices datasets utils methods base
loaded via a namespace (and not attached):
 grid_2.8.1 lattice_0.17-20 lme4_0.999375-28
On Tue, 17 Mar 2009 06:53:20 +0000, Emmanuel Charpentier wrote :
> Dear list,
> "+" (and "-") being defined for difftime class, I expected mean() to
> return something sensible. This is only half-true :
>> mean(c(1:5, 5:1),na.rm=TRUE)
>  3
>> mean(as.difftime(c(1:5, 5:1),unit="mins"),na.rm=TRUE)
> Time difference of 3 mins
> Fine so far. However :
>> mean(c(1:5, NA,5:1),na.rm=TRUE)
>  3
>> mean(as.difftime(c(1:5, NA,5:1),unit="mins"),na.rm=TRUE)
> Time difference of NA mins
> Ouch !
> Curiously, var(), max() and min() behave as expected. What's so special
> with mean() ?
>> RSiteSearch("mean difftime")
> [ ... doesn't return anything relevant ]
> NB : this isn't done for the hell of it. I intended to replace some
> missing dates, with something computed from other dates and mean time
> Any thoughs ?
> Emmanuel Charpentier
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