[R] is.na for S4 object

[Martin Maechler]

>>>>> Martin Morgan <mtmorgan at fredhutch.org>
>>>>>     on Thu, 4 Jun 2015 10:33:37 -0700 writes:

    > On 06/04/2015 10:08 AM, cgenolin wrote:
    >> Hi the list,
    >> 
    >> I have a variable y that is either NA or some S4 object. I would like to
    >> know in which case I am, but it seems taht is.na does not work with S4
    >> object, I get a warnings:
    >> 
    >> --- 8< ------------
    >> setClass("myClass",slots=c(x="numeric"))
    >> if(runif(1)>0.5){a <- new("myClass")}else{a <- NA}
    >> is.na(a)
    >> --- 8< ------------
    >> 
    >> Any solution?

    > getGeneric("is.na")

    > shows that it's an S4 generic, so implement a method

    > setMethod("is.na", "myClass", function(x) FALSE)

    > Martin

For the present special case though,  a more efficient solution would be
to use  isS4(.)  instead of  !is.na(.)

another Martin 


    >> Thanks
    >> Christophe