From: Petr PIKAL <petr.pikal_at_precheza.cz>

Date: Tue, 04 Mar 2008 13:20:48 +0100

R-help_at_r-project.org mailing list

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

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
**> 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.

R-help_at_r-project.org mailing list

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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