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

round(abs(0.95 - 1),2) > 0.05

round(abs(0.95 - 1),2) < 0.05

-----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 Du?a <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 Du?a
<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