[R] match() & seq()

[Petr Pikal]

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
> >>
> >>    
> >>
> >
> >  
> >
> 
> ______________________________________________
> 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

Petr Pikal
petr.pikal at precheza.cz