Zoo - bug ???

I am not sure whether this is 100 % related, but I also get some unexpected
behaviour with NA and rollapply:
In the following example I would expect in Line 3 to see a 1 instead of an
NA (mean out of [1, NA, NA]
What do you think ?

mean(c(1,NA, NA), na.rm=TRUE)

[1] 1

A1a<-zoo(c(NA, NA, 1,2,3,4,5,6, NA, NA))
A1b<-rollapply(A1a,4,mean, na.rm=TRUE, na.pad=FALSE, align="right")
View(cbind(A1a,A1b))
cbind(A1a,A1b)

A1a A1b
1   NA  NA
2   NA  NA
3    1  NA
4    2 1.5
5    3 2.0
6    4 2.5
7    5 3.5
8    6 4.5
9   NA 5.0
10  NA 5.5

-----
Christian Langkamp
christian.langkamp-at-gmxpro.de

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