[R] Department of Redundancy Department.

[Liaw, Andy]

I couldn't resist, either... 

> From: Henrik Bengtsson
> 
> Hmm,
> 
> couldn't resists:
> 
> > X <- NA
> > is.logical(X)
> [1] TRUE
> > (X == TRUE)
> [1] NA
> 
> > "==.MaybeNA" <- function(e1, e2) { !is.na(e1) && (e1 == e2) }
> > X <- structure(NA, class="MaybeNA")
> > is.logical(X)
> [1] TRUE
> > (X == TRUE)
> [1] FALSE
> 
> Ta da ;)

But anything compared to NA should result in NA!

Andy

 
> Henrik
> 
> PS. It might be worth mentioning base::isTRUE() when we're 
> already at it. DS.
> 
> 
> On Thu, Aug 14, 2008 at 3:07 PM, Rolf Turner 
> <r.turner at auckland.ac.nz> wrote:
> >
> > I just noticed a certain ``usage'' in a recent posting, and couldn't
> > restrain my self from commenting.  The usage was of the form
> >
> >        ``if(X==TRUE)''
> >
> > where X was a logical variable.
> >
> > This sort of thing is brought to you by your Department of 
> Redundancy
> > Department.  The ``==TRUE'' bit is irrelevant, incompetent, 
> and immaterial,
> > as Perry Mason used to say.  The value of X==TRUE is 
> exactly the same as
> > the value of X when X is a logical variable.  If X is not a 
> logical variable
> > a lot of strange things can happen, depending on the nature of X.
> >
> > It is safer and takes 6 fewer key strokes to use ``if(X)''. 
>  So why not
> > do that, eh?
> >
> >        cheers,
> >
> >                Rolf Turner
> >
> > P. S.  The example that triggered this post actually used 
> ``if(X==T)''.
> > This is doubly dangerous since ``T'' can be overwritten.  If it was
> > overwritten you'd get toadally wrong answers.  E.g., suppose you had
> > set
> >
> >        T <- FALSE   # !!!
> >
> > ***ALWAYS USE ``TRUE'' AND ``FALSE'' FOR LOGICAL VALUES.
> >   DO NOT USE ``T'' AND ``F''.***
> >
> > 
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> 
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