Re: [R] is.na behavior

I am not sure I undestand the issue. But if the question is to decidedif an expression evaluates to NA, using eval should solve the problem. In fact, I do not really understand what an NA expression, and not an expression evaluating to NA, means. signature.asc Description: Message signed with

Re: [R] is.na behavior

I don't think the question is about what an expression evaluates to, but what it is. I don't think it makes sense for an expression to be NA, but I am not a language designer. The expression NA tells the compiler that a literal NA_logical_ value is to be returned from evaluating that

Re: [R] is.na behavior

Richard, I think the reason that this gives the warning is for the rest of us who don't think about asking about missing values in non-data objects. I could imagine someone choosing a poor name for a variable and doing something like: mean <- mean(x) is.na(mean) which would then tell them

Re: [R] is.na behavior

> On Nov 18, 2015, at 5:54 PM, Richard M. Heiberger 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’

Re: [R] is.na behavior

David, Your answer begs the question. What is the problem with non-(list or vector) of type language. To my eye both expression(abcd) and call("mean") look like they have non-missing values, hence I anticipated that they are not NA, and therefore that is.na() would return FALSE without a warning.

[R] is.na behavior

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]]

Re: [R] is.na behavior

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

Re: [R] is.na behavior

It is in context of determining if an input argument for a graph title is missing or null or na. In any of those cases the function defines a main title. If the incoming title is not one of those, then I use the incoming title. When the incoming title is an expression I see the warning.

Re: [R] is.na behavior

Maybe the way to rephrase my question is to ask why there is not an is.na.expression method that does that task for me? > is.na(as.list(expression("defg"))) [1] FALSE > is.na(expression("defg")) [1] FALSE Warning message: In is.na(expression("defg")) : is.na() applied to non-(list or vector) of