[R] Help with NaN when 0 divided by 0

[William Dunlap]

>  "%/0%" <- function(x,y) { res <- x / y ; res[ is.na(res) ] <- 0;
> return(res) }

I think this would be more to the point if the output were set to 0
if the numerator were 0, not if the output would be NA. 
   res[x==0] <-0

You may also want to restructure your computations so that
the proportion resulting from 0/0 remains as NaN but when
you multiply the proportion by a total you set the result to be 0
if the total is 0.  (If the total is not 0 you may want to signal
an error.)

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 Jennifer Sabatier
> Sent: Wednesday, August 01, 2012 7:18 AM
> To: David Winsemius
> Cc: r-help at r-project.org
> Subject: Re: [R] Help with NaN when 0 divided by 0
> 
> Hi Everyone,
> 
> Thanks so much for all your suggestions!  All of these worked but David's
> was best suited for my purposes, considering it was something happens
> sporadically.
> 
> I don't do expenditure analyses often as I mostly do run of the mill survey
> analysis, but this will come in handy for the once or twice a year I do
> this.
> 
> Jen
> 
> On Tue, Jul 31, 2012 at 5:19 PM, David Winsemius <dwinsemius at comcast.net>wrote:
> 
> >
> > On Jul 31, 2012, at 1:23 PM, Jennifer Sabatier wrote:
> >
> >  Hi All,
> >>
> >>
> >>
> >> I have some data where I am doing fairly simple calculations, nothing more
> >> than adding, subtracting, multiplying and dividing.
> >>
> >>
> >>
> >> I'm running into a problem when I divide one variable by another and when
> >> they're both 0 I get NaN. I realize that if you divide a non-zero by 0
> >> then
> >> you get Inf, which is, of course, correct.  But in my case I never get
> >> Inf,
> >> just NaN because of the structure of my dataset.
> >>
> >>
> >>
> >> Here's a dumb example:
> >>
> >>
> >>
> >> var1 <- c(0, 500, 5379, 0, 1500, 1750)
> >>
> >> var2 <- c(0, 36, 100, 0, 10, 5)
> >>
> >>
> >>
> >> var1/var2
> >>
> >>
> > It's possible to define new infix operators (although I have forgotten
> > which help page describes this in more detail and I cannot seem to find it
> > right now):
> >
> >  "%/0%" <- function(x,y) { res <- x / y ; res[ is.na(res) ] <- 0;
> > return(res) }
> >
> > # You cannot use %/% because it is already used for integer division. I
> > guess you could use "//", but to me that looks too much like "||" which is
> > the single-value-OR. You could also use "%div0%".
> >
> >  var1 %/0% var2
> >
> > #[1]   0.00000  13.88889  53.79000   0.00000 150.00000 350.00000
> >
> > If this is a regular need, you can put this in a .profile file or a
> > package. See:
> >
> > ?Startup
> >
> > --
> >
> >  I realize the NaNs are logical, but for my purposes this should just be 0
> >> because I am calculating expenditures and if you spent no money in one
> >> sub-area and none in the whole area then you don't have an expenditure at
> >> all, so it should be 0.  And since R doesn't like adding NA's or NaN's to
> >> anything, I'd rather just have this be 0 so that my future calculations,
> >> such as adding up expenditure, is simple.
> >>
> >>
> >> Is there an easy way to avoid the NaN's, something a non-programmer (ie,
> >> the person I am handing this code off to) would understand?
> >>
> >
> >
> >
> >>
> >> Thanks,
> >>
> >>
> >> Jen
> >>
> >>         [[alternative HTML version deleted]]
> >>
> >> ______________________________**________________
> >> R-help at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/**listinfo/r-
> help<https://stat.ethz.ch/mailman/listinfo/r-help>
> >> PLEASE do read the posting guide http://www.R-project.org/**
> >> posting-guide.html <http://www.R-project.org/posting-guide.html>
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> > David Winsemius, MD
> > Alameda, CA, USA
> >
> >
> 
> 	[[alternative HTML version deleted]]