Adrian Alexa <[EMAIL PROTECTED]> writes:
>
> I have observed that is.na() behaves strange on some lists. Here is a
> simple example:
>
>
> > a = list(list('asd'))
> > a
> [[1]]
> [[1]][[1]]
> [1] "asd"
>
>
> > for(i in 1:5)
> + print(is.na(a))
> [1] TRUE
> [1] FALSE
> [1] TRUE
> [1] TRUE
> [1] TRUE
> >
>
> [...snip...]
>
> In my view this seems to be a bug. If is not, can somebody explain me what is
> really happening and how can I overcome this behavior?
This looks like a bug to me. As far as a workaround goes you
could try this:
is.na <- function(x)
if (length(x) == 0) {
mode(x) <- "logical"
x
} else if (inherits(x, "list")) {
lapply(x, function(i) if (is.atomic(x)) base::is.na(x) else FALSE)
} else
base::is.na(x)
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