Re: [R] help for the first poster- a simple question

From: Petr PIKAL <petr.pikal_at_precheza.cz>
Date: Tue, 04 Mar 2008 13:20:48 +0100

Hi

r-help-bounces_at_r-project.org napsal dne 03.03.2008 20:12:34:

> Thanks for all response. Here is more closer to my question,
> p<-0.05
>
> f<-0.05
>
> ld<-sqrt(f* (1 - f) * p * (1 - p))
>
> D <- (p * (1 - f) - ld)/p
>
> d <- ((1 - p) * f - ld)/(1 - p)
>
> haplo<-data.frame(D,d)
>
> > haplo
> D d
> 1 -1.387779e-16 -7.304099e-18
>
> cond1<-pmin(haplo[,1],haplo[,2])
>
> haplo[cond1>=0,]

Either do not use computers as they sometimes can not represent exactly fractional values. Or use rounding,
haplo[round(cond1, 10)>=0,]

Regards
Petr

>
> But the program cannot get right one, because
>
>
> -1.387779e-16>=0 is FALSE
>
> -7.304099e-18>=0 is FALSE
>
>
>
> Thank you!
>
> xj.
>
>
> ----- Original Message -----
> From: "Gavin Simpson" <gavin.simpson_at_ucl.ac.uk>
> To: "Xuejun Qin" <xjq_at_chg.duhs.duke.edu>
> Cc: <r-help_at_r-project.org>
> Sent: Monday, March 03, 2008 12:57 PM
> Subject: Re: [R] help for the first poster- a simple question
>
>
> > On Mon, 2008-03-03 at 12:52 -0500, Xuejun Qin wrote:
> >> Hi, there,
> >> I cannot get accurate value for calculation.
> >> for example:
> >> ld<-
> >> 0.05*0.95-ld=-6.938894e-18
> >> 0.05*0.95-ld==0 is False.
> >>
> >> I met this problem in my program, how can I handle it. Thanks.
> >
> > Answer 1:
> >
> > Read FAQ 7.31 -
> >
> >
http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-

> numbers-are-equal_003f
> >
> > Answer 2:
> >
> > Use all.equal()
> >
> >> ld<-sqrt(1*0.05*0.95*0.05*0.95)
> >> 0.05*0.95-ld
> > [1] -6.938894e-18
> >> 0.05*0.95-ld==0
> > [1] FALSE
> >> all.equal(0.05*0.95-ld, 0)
> > [1] TRUE
> >
> >>
> >>
> >> xj.
> >
> > HTH
> >
> > G
> > --
> > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
> > Dr. Gavin Simpson [t] +44 (0)20 7679 0522
> > ECRC, UCL Geography, [f] +44 (0)20 7679 0565
> > Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk
> > Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/
> > UK. WC1E 6BT. [w] http://www.freshwaters.org.uk
> > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
> >
> >
>
> ______________________________________________
> R-help_at_r-project.org mailing list
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> 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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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. Received on Tue 04 Mar 2008 - 12:35:55 GMT

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