[R] "NA-friendly" operator

[William Dunlap]

Instead of ignore-NA versions of ">", "<", "==", etc., I prefer to factor out
the ignore-NA part of things:

   is.true <- function(x) !is.na(x) & x
   is.false <- function(x) !is.na(x) & !x
used as
  >  is.false(c(1,2,NA,4) > 3)
  [1]  TRUE  TRUE FALSE FALSE
  >    is.true(c(1,2,NA,4) > 3)
  [1] FALSE FALSE FALSE  TRUE
or with any other expression that evaluates to a logical.

subset() must have a similar thing buried in it and people use it for that but
then get caught up in its nonstandard evaluation semantics.  which() must
also have it but you don't always want to convert to integer indexes.

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 Berend Hasselman
> Sent: Tuesday, October 30, 2012 2:26 PM
> To: vincent guyader
> Cc: r-help at r-project.org
> Subject: Re: [R] "NA-friendly" operator
> 
> 
> On 30-10-2012, at 22:08, vincent guyader wrote:
> 
> > Hi everyone,
> >
> > i'm looking for a "NA-friendly" operator
> >
> > I explain :
> >
> >        vec<-c(3,4,5,NA,1,NA,9,NA,1)
> >
> >        vec[vec == 1]  # NA  1 NA NA  1
> >
> > I dont want the NA's :
> >        vec[vec == 1 & ! is.na(vec)]# 1  1
> > is the same as
> >        vec[vec %in% 1] # 1  1
> >
> > %in% is NA-friendly :)
> >
> > But if i want >2 without the NA's :
> >
> >        vec[vec>2] #3  4  5 NA NA  9 NA
> >
> > if i dont want the NA i have to do :
> >
> >        vec[vec>2 & !is.na(vec)] #3  4  5  9
> >
> > is there an opérator to directly do that?
> 
> 
> You could define one
> 
>  "%>.nona%" <- function(x,y) x[x>y & !is.na(vec)]
> 
> and use
> 
>  vec %>.nona% 2
> 
> Use  ?`%in%` to see an example (in the Examples section)
> 
> Berend
> 
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