help for the first poster- a simple question

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,]

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 -

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
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