[R] match() & seq()
Petr Pikal
petr.pikal at precheza.cz
Tue Jan 31 09:09:13 CET 2006
Hi
?identical
The safe and reliable way to test two objects for being _exactly_
^^^^^^^^^
equal. It returns 'TRUE' in this case, 'FALSE' in every other
case.
?all.equal
'all.equal(x,y)' is a utility to compare R objects 'x' and 'y'
testing "near equality". If they are different, comparison is
^^^^^^^^^^^
still made to some extent, and a report of the differences is
HTH
Petr
On 31 Jan 2006 at 11:21, Jacques VESLOT wrote:
Date sent: Tue, 31 Jan 2006 11:21:20 +0400
From: Jacques VESLOT <jacques.veslot at cirad.fr>
To: Roger.Bivand at nhh.no
Copies to: R-help at stat.math.ethz.ch
Subject: Re: [R] match() & seq()
> Thanks Roger, Andy and Dimitris...
> though i am familiar with this behaviour **in some cases**, i couldn't
> catch - yesterday evening - why it matched with 0.4, and not with 0.3;
> of course these numbers are not integers ! but i believed match()
> deals with such equalities. i will have a look at the article
> mentionned in FAQ 7.31 since everything is not clear for me yet .
> > identical(0.4-0.3,0.1)
> [1] FALSE
> > all.equal(0.4-0.3,0.1)
> [1] TRUE
>
> jacques
>
>
> Roger Bivand a écrit :
>
> >On Mon, 30 Jan 2006, Jacques VESLOT wrote:
> >
> >
> >
> >>sorry if it has already been discussed but i can't understand this:
> >>
> >> > seq(0.1,1,by=0.1)
> >> [1] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
> >> > match(0.1,seq(0.1,1,by=0.1))
> >>[1] 1
> >> > match(0.2,seq(0.1,1,by=0.1))
> >>[1] 2
> >> > match(0.3,seq(0.1,1,by=0.1))
> >>[1] NA
> >> > match(0.4,seq(0.1,1,by=0.1))
> >>[1] 4
> >>
> >>
> >
> >FAQ 7.31
> >http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-
> >these-numbers-are-equal_003f
> >
> >
> >
> >>print(seq(0.1,1,by=0.1), digits=20)
> >>
> >>
> > [1] 0.10000000000000000555 0.20000000000000001110
> > 0.30000000000000004441 [4] 0.40000000000000002220
> > 0.50000000000000000000 0.59999999999999997780 [7]
> > 0.70000000000000006661 0.80000000000000004441 0.90000000000000002220
> >[10] 1.00000000000000000000
> >
> >
> >>match(c(0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9), seq(0.1,1,by=0.1))
> >>
> >>
> >[1] 1 2 NA 4 5 6 NA 8 9
> >
> >
> >>all.equal(c(0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0),
> >>seq(0.1,1,by=0.1),
> >>
> >>
> >+ tolerance = .Machine$double.eps ^ 2)
> >[1] "Mean relative difference: 1.665335e-16"
> >
> >
> >>all.equal(c(0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0),
> >>seq(0.1,1,by=0.1))
> >>
> >>
> >[1] TRUE
> >
> >
> >
> >
> >> > R.version
> >> _
> >>platform i386-pc-mingw32
> >>arch i386
> >>os mingw32
> >>system i386, mingw32
> >>status
> >>major 2
> >>minor 2.1
> >>year 2005
> >>month 12
> >>day 20
> >>svn rev 36812
> >>language R
> >>
> >>______________________________________________
> >>R-help at stat.math.ethz.ch mailing list
> >>https://stat.ethz.ch/mailman/listinfo/r-help
> >>PLEASE do read the posting guide!
> >>http://www.R-project.org/posting-guide.html
> >>
> >>
> >>
> >
> >
> >
>
> ______________________________________________
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> PLEASE do read the posting guide!
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Petr Pikal
petr.pikal at precheza.cz
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