[R] Extending a vector to length n

[hadley wickham]

In general, how can I increase a vector of length m (< n) to length n
by padding it with m - n missing values, without losing attributes?
The two approaches I've tried, using length<- and adding missings with
c, do not work in general:

> a <- as.Date("2008-01-01")
> c(a, NA)
[1] "2008-01-01" NA
> length(a) <- 2
> a
[1] 13879    NA


> b <- factor("a")
> c(b, NA)
[1]  1 NA
> length(b) <- 2
> b
[1] a    <NA>
Levels: a

Hadley



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