On Tue, Jul 13, 2010 at 5:27 PM, Gavin Simpson <gavin.simpson@ucl.ac.uk>wrote:

> On Tue, 2010-07-13 at 17:13 +0530, sayan dasgupta wrote:
> > Hi folks,
> >
> > I am confused whether the following is a bug or it is fine
> >
> > Here is the explanation
> >
> > a <- zoo(c(NA,1:9),1:10)
> >
> > Now If I do
> >
> > rollapply(a,FUN=mean,width=3,align="right")
>
> mean() has argument na.rm which defaults to FALSE. As such, if NA are in
> the computation the mean is undefined and the answer will be NA. If you
> pass na.rm = TRUE to rollapply, mean ignores the NA and works on the
> remaining values:
>
> > rollapply(a,FUN=mean,width=3,align="right", na.rm = TRUE)
>   3   4   5   6   7   8   9  10
> 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0
>

This is fine but the problem is logically when you are doing rollapply only
the first 2 values should be NA
but suppose for index 10 as I have mentioned the rollapply should be a mean
of b9, 8 ,7 and there is no NA here.
So it should not return NA






>
> HTH
>
> G
>
> >
> > I get
> > > rollapply(a,FUN=mean,width=3,align="right")
> >  3  4  5  6  7  8  9 10
> > NA NA NA NA NA NA NA NA
> >
> > But I shouldn't be getting NA right ? i.e for index 10 I should get
> > (1/3)*(9+8+7)
> >
> > Similarly
> >
> > > rollapply(a,FUN=mean,width=3)
> >  2  3  4  5  6  7  8  9
> > NA NA NA NA NA NA NA NA
> >
> >
> > Zoo version :
> >
> > > installed.packages()["zoo","Version"]
> > [1] "1.6-3"
> > >
> >
> >
> > My machine details
> >
> > > sessionInfo()
> > R version 2.10.1 (2009-12-14)
> > i386-pc-intel32
> >
> > locale:
> > [1] LC_COLLATE=English_India.1252  LC_CTYPE=English_India.1252
> > LC_MONETARY=English_India.1252 LC_NUMERIC=C
> > [5] LC_TIME=English_India.1252
> >
> > attached base packages:
> > [1] stats     graphics  grDevices datasets  utils     methods   base
> >
> > other attached packages:
> > [1] zoo_1.6-3      rcom_2.2-1     rscproxy_1.3-1 Revobase_3.2.0
> >
> > loaded via a namespace (and not attached):
> > [1] grid_2.10.1    lattice_0.18-3 tools_2.10.1
> > >
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
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> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> --
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>  Dr. Gavin Simpson             [t] +44 (0)20 7679 0522
>  ECRC, UCL Geography,          [f] +44 (0)20 7679 0565
>  Pearson Building,             [e] gavin.simpsonATNOSPAMucl.ac.uk
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