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

From: Marianne Promberger <mpromber_at_psych.upenn.edu>
Date: Mon, 03 Mar 2008 18:49:54 +0000

On 03/03/08 12:52, Xuejun Qin wrote:
> Hi, there,
> I cannot get accurate value for calculation.
> for example:
> ld<-sqrt(1*0.05*0.95*0.05*0.95)
> 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.

I think what you are experiencing is this: http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f

(R FAQ "7.31 Why doesn't R think these numbers are equal?")

Maybe handle it using round().

HTH m.



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