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''.***
######################################################################
Attention:\ This e-mail message is privileged and confid...{{dropped:9}}
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 ;) 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''.*** > > ###################################################################### > Attention:\ This e-mail message is privileged and confid...{{dropped:9}} > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >
Look at:> library(fortunes) > fortune(69)-- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.snow at imail.org (801) 408-8111> -----Original Message----- > From: r-help-bounces at r-project.org > [mailto:r-help-bounces at r-project.org] On Behalf Of Rolf Turner > Sent: Thursday, August 14, 2008 4:07 PM > To: R-help Forum > Subject: [R] Department of Redundancy Department. > > > 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''.*** > > ###################################################################### > Attention:\ This e-mail message is privileged and > confid...{{dropped:9}} > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >