[Rd] potential r bug (floor)

Duncan Murdoch murdoch at stats.uwo.ca
Tue Jun 24 17:59:49 MEST 2003

On Tue, 24 Jun 2003 15:26:56 -0400, "kjetil brinchmann halvorsen"
<kjetil at entelnet.bo> wrote in message <3EF86DC0.5086.57E9D at localhost>:

>On 23 Jun 2003 at 20:20, Prof Brian D Ripley wrote:

>> BTW, on my Windows XP machine I do get
>> > floor(log10(1000))
>> [1] 3
>On my windows XP machine (R1.7.1) i get:
>> floor( log10(1000) )
>[1] 2
>Why this difference between different XP machines?

I can guess two possibilities:  

1.  One of you is using the binary I compiled, the other is using
something different.  Since mine shows 2 as the answer, I think Kjetil
might be using mine.

2.  One of you has had the floating point precision reduced by some
buggy DLL or video driver.  

There are probably other explanations. The calculation is inherently
unstable; it might be that Brian did it under a different phase of the
moon, and that's why he got the "right" answer.

Duncan Murdoch

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