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MathGroup Archive 2007

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Re: strange rounding result

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80967] Re: [mg80918] strange rounding result
  • From: Syd Geraghty <sydgeraghty at mac.com>
  • Date: Thu, 6 Sep 2007 05:34:37 -0400 (EDT)
  • References: <200709050659.CAA27251@smc.vnet.net>

Chris... This appears to be a bug in Round.

I tried:-

In[27]:= Round[9.995, 1/100]
Round[%]
Out[27]= 999/100
Out[28]= 10

In[26]:= Round[999/100]
Out[26]= 10

So the Round of the "interim" result gave the expected integer result.

Cheers ... Syd
On Sep 4, 2007, at 11:59 PM, Chris Chiasson wrote:

> Round[9995,10]
> Round[999.5,1]
> Round[99.95,1/10]
> Round[9.995,1/100]
> Round[.9995,1/1000]
>
> The results of these commands are decreasing powers of ten, except the
> second to last one, which gives 999/100 on my machine. I assume it has
> something to do with the storage of floating point numbers in binary
> rather than decimal form, but I don't know. Anyway, it just seemed
> strange to me and I wanted to point it out.
>
> Maybe it has something to do with the "round to even" behavior? Meh.
>
> -- 
> http://chris.chiasson.name/
>



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