[R] Problem with <= (less than or equal): not giving the expected result
Adrian Dușa
dusa.adrian at unibuc.ro
Tue Apr 5 14:31:20 CEST 2016
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(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>
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
> ______________________________________________
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--
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania
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