[R] binary operators that never return missing values

[William Dunlap]

The following function expects a logical input and maps NA entries to FALSE:
   is.true <- function(x) !is.na(x) & x
E.g.,
  > z <- c(1,2,3,NA,5,6)
  > is.true(z>2.5 & z<5.5)
  [1] FALSE FALSE  TRUE FALSE  TRUE FALSE

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Anthony Damico
> Sent: Wednesday, June 20, 2012 2:19 PM
> To: R. Michael Weylandt
> Cc: r-help at r-project.org
> Subject: Re: [R] binary operators that never return missing values
> 
> Thanks Michael,
> 
> I was hoping to complete this in one step (since I use these a lot).
> Setting the class of the vectors seems like more typing than just
> doing %>F%  ...
> 
> Unfortunately, my knowledge of classes, methods, and the like is
> pretty shaky.  Is it possible to *create* another set of operators
> that just changes NAs to falses or trues?--
> 
> >F  <F  >=F  <=F  >T  <T  >=T  <=T
> 
> I definitely don't want to change the base functionality of the
> operators, so infix notation seems like the strategy that will require
> the least typing in the long run..  but my mind is still open. :)
> 
> 
> 
> On Wed, Jun 20, 2012 at 4:54 PM, R. Michael Weylandt
> <michael.weylandt at gmail.com> wrote:
> > Hi Anthony,
> >
> > No, I don't believe this exists on CRAN already (happy to be proven
> > wrong though) but I might suggest you approach things a different way:
> > instead of defining this operator by operator with infix notation, why
> > not go after `+`, `>` directly? If you put a class on your vectors,
> > you can define Ops.class which will change the behavior of all those
> > sorts of things.
> >
> > Simple example (probably not complete nor necessarily advisable)
> >
> > a <- c( 1 , NA , 7 , 2 , NA )
> > b <- c( NA , NA , 9 , 1 , 6 )
> >
> > class(a) <- class(b) <- "damico"
> >
> > Ops.damico <- function(e1, e2 = NULL){
> >    e1[is.na(e1)] <- 0
> >    e2[is.na(e2)] <- 0
> >    NextMethod()
> > }
> >
> > a < b
> >
> > More nuance is available, but this hopefully gives you a start. You
> > might, e.g., think about setting this as something more like:
> >
> > Ops.damico <- function(e1, e2 = NULL){
> >    if(.Generic %in% c("==","!=","<","<=",">=",">")){
> >        e1[is.na(e1)] <- 0
> >        e2[is.na(e2)] <- 0
> >    }
> >    NextMethod()
> > }
> >
> > so you don't mess up arithmetic but only the boolean comparisons.
> >
> > Best,
> > Michael
> >
> > On Wed, Jun 20, 2012 at 3:44 PM, Anthony Damico <ajdamico at gmail.com> wrote:
> >> Hi, I work with data sets with lots of missing values.  We often need
> >> to conduct logical tests on numeric vectors containing missing values.
> >>  I've searched around for material and conversations on this topic,
> >> but I'm having a hard time finding anything.  Has anyone written a
> >> package that deals with this sort of thing?  All I want are a group of
> >> functions like the ones I've posted below, but I'm worried I'm
> >> re-inventing the wheel..  If they're not already on CRAN, I feel like
> >> I should add them.  Any pointers to work already completed on this
> >> subject would be appreciated.  Thanks!
> >>
> >> Anthony Damico
> >> Kaiser Family Foundation
> >>
> >>
> >>
> >> Here's a simple example of what I need done on a regular basis:
> >>
> >> #two numeric vectors
> >> a <- c( 1 , NA , 7 , 2 , NA )
> >>
> >> b <- c( NA , NA , 9 , 1 , 6 )
> >>
> >> #this has lots of NAs
> >> a > b
> >>
> >> #save this result in x
> >> x <- (a > b)
> >>
> >> #overwrite NAs in x with falses (which we do a lot)
> >> x <- ifelse( is.na( x ) , F , x )
> >>
> >> #now x has only trues and falses
> >> x
> >>
> >>
> >>
> >> ################
> >> Here's an example function that solves the problem for "greater than"
> >> ################
> >>
> >>
> >> #construct a function that performs the same steps:
> >> "%>F%" <-
> >>        function( a , b ){
> >>
> >>                x <- (a > b)
> >>
> >>                x.false <- ifelse( is.na( x ) , F , x )
> >>
> >>                x.false
> >>
> >>        }
> >>
> >> #run the function
> >>
> >> a %>F% b
> >>
> >> ______________________________________________
> >> 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.
> 
> ______________________________________________
> 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.