You can convert the expression to a list and use is.na on that:
> e <- expression(1+NA, NA, 7, function(x)x+1)
> is.na(as.list(e))
[1] FALSE TRUE FALSE FALSE
and you can do the same for a call object
> is.na(as.list(quote(func(arg1, tag2=NA, tag3=log(NA)))))
tag2 tag3
FALSE FALSE TRUE FALSE
However, what is your motivation for wanting to apply is.na to an expression?
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Wed, Nov 18, 2015 at 5:54 PM, Richard M. Heiberger <r...@temple.edu> wrote:
> What is the rationale for the following warning in R-3.2.2?
>
>> is.na(expression(abcd))
> [1] FALSE
> Warning message:
> In is.na(expression(abcd)) :
> is.na() applied to non-(list or vector) of type 'expression'
>
> [[alternative HTML version deleted]]
>
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