[R] Problem with <= (less than or equal): not giving the expected result

[PIKAL Petr]

Hi

Or some rounding when comparing results with threshold exactly.

> round(abs(0.95 - 1),2) > 0.05
[1] FALSE
> round(abs(0.95 - 1),2) < 0.05
[1] FALSE
>
Cheers
Petr

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Rainer
> Johannes
> Sent: Tuesday, April 5, 2016 4:33 PM
> To: Thierry Onkelinx <thierry.onkelinx at inbo.be>
> Cc: r-help at r-project.org; Adrian Dușa <dusa.adrian at unibuc.ro>
> Subject: Re: [R] Problem with <= (less than or equal): not giving the expected
> result
>
> Thanks!
>
> On 05 Apr 2016, at 16:07, Thierry Onkelinx
> <thierry.onkelinx at inbo.be<mailto:thierry.onkelinx at inbo.be>> wrote:
>
> You could use something like this
>
> x <- abs(0.95 - 1)
> treshold <- 0.05
> x < treshold | abs(x - treshold) < 1e-6
>
>
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
> Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality
> Assurance Kliniekstraat 25
> 1070 Anderlecht
> Belgium
>
> To call in the statistician after the experiment is done may be no more than
> asking him to perform a post-mortem examination: he may be able to say
> what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of
> anecdote is not data. ~ Roger Brinner The combination of some data and an
> aching desire for an answer does not ensure that a reasonable answer can be
> extracted from a given body of data. ~ John Tukey
>
> 2016-04-05 14:46 GMT+02:00 Rainer Johannes
> <Johannes.Rainer at eurac.edu<mailto:Johannes.Rainer at eurac.edu>>:
> Thanks Adrian and Thierry (from the previous answer).
>
> I was aware of the all.equal function, but there is nothing similar for <= (e.g.
> all.smallerEqual)?
>
> cheers, jo
>
> On 05 Apr 2016, at 14:31, Adrian Dușa
> <dusa.adrian at unibuc.ro<mailto:dusa.adrian at unibuc.ro><mailto:dusa.adria
> n at unibuc.ro<mailto:dusa.adrian at unibuc.ro>>> wrote:
>
> Yes, that does have to do with floating point representation.
> I use this function for these types of comparisons (works with values as well
> as with vectors):
>
> check.equal <- function(x, y) {
>     check.vector <- as.logical(unlist(lapply(x, all.equal, y)))
>     check.vector[is.na<http://is.na/><http://is.na/>(check.vector)] <- FALSE
>     return(check.vector)
> }
>
> See:
> ?all.equal
>
> Hth,
> Adrian
>
> On Tue, Apr 5, 2016 at 2:34 PM, Rainer Johannes
> <Johannes.Rainer at eurac.edu<mailto:Johannes.Rainer at eurac.edu><mailto:
> Johannes.Rainer at eurac.edu<mailto:Johannes.Rainer at eurac.edu>>> wrote:
> Dear All,
>
> I have the following problem:
>
> I have a function in which I check if the difference between values is smaller
> or equal to a certain threshold. I however realized that I might get there
> some unexpected results:
>
> > abs(1 - 0.95) >= 0.05
> [1] TRUE
> ## So that’s fine, but:
> > abs(1 - 0.95) <= 0.05
> [1] FALSE
>
> Apparently, abs(1 - 0.95) is not equal to 0.05, which I find however quite
> disturbing.
>
> Along these lines:
> > abs(0.95 - 1) > 0.05
> [1] TRUE
> > abs(0.95 - 1) < 0.05
> [1] FALSE
>
> I guess that has to do with the floating point representation of the data?
>
> Is there something I miss or is there any solution to this?
> Thanks for any help!
>
> cheers, jo
>
>
>
> I tried this on different R-version (including 3.2.3 and 3.3.0 alpha); The R-
> version I used for the code above is:
>
> > sessionInfo()
> R version 3.0.2 (2013-09-25)
> Platform: x86_64-unknown-linux-gnu (64-bit)
>
> locale:
>  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
>  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
>  [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
>  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
>  [9] LC_ADDRESS=C               LC_TELEPHONE=C
> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> ______________________________________________
> R-help at r-project.org<mailto:R-help at r-project.org><mailto:R-help at r-
> project.org<mailto:R-help at r-project.org>> mailing list -- To UNSUBSCRIBE
> and more, see 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><http://www.r-
> project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
>
>
> --
> Adrian Dusa
> University of Bucharest
> Romanian Social Data Archive
> Soseaua Panduri nr.90
> 050663 Bucharest sector 5
> Romania
>
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org<mailto:R-help at r-project.org> mailing list -- To
> UNSUBSCRIBE and more, see 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.
>
>
>
>       [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.

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