

Full_Name: Matthew Davis
Version: 2.2.0
OS: OS X (10.4.5)
Submission from: (NULL) (209.107.120.195)
the mean of my sample x is 0.2, and when I check mean(x)<=0.2 I get a TRUE
value, when I check mean(x)<=(10.8) I get a FALSE value. (x < c(0, 1, 0, 0,
0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0))
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> 0.2==(10.8)
[1] FALSE
On Mar 12, 2006, at 15:39 , [hidden email] wrote:
> Full_Name: Matthew Davis
> Version: 2.2.0
> OS: OS X (10.4.5)
> Submission from: (NULL) (209.107.120.195)
>
>
> the mean of my sample x is 0.2, and when I check mean(x)<=0.2 I get
> a TRUE
> value, when I check mean(x)<=(10.8) I get a FALSE value. (x < c
> (0, 1, 0, 0,
> 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0))
>
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> https://stat.ethz.ch/mailman/listinfo/rdevel>
===
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On 3/12/2006 6:39 PM, [hidden email] wrote:
> Full_Name: Matthew Davis
> Version: 2.2.0
> OS: OS X (10.4.5)
> Submission from: (NULL) (209.107.120.195)
>
>
> the mean of my sample x is 0.2, and when I check mean(x)<=0.2 I get a TRUE
> value, when I check mean(x)<=(10.8) I get a FALSE value. (x < c(0, 1, 0, 0,
> 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0))
Why make this so complicated? The natural conclusion from that is that
0.2 is not equal to (10.8), and indeed:
> (10.8) == 0.2
[1] FALSE
The problem is that neither 0.2 nor 0.8 can be represented exactly, so
when you do calculations using them you are doing approximations. The
approximation involving your mean is different than the one involving
(10.8). This is an FAQ,
7.31 Why doesn't R think these numbers are equal?
This is not a bug.
Duncan Murdoch
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However, mean(x)==0.2 returns TRUE
Also, mean(x)>=(10.8) returns TRUE ;)
So, it's not just the approximation calculus.
On Sun, 12 Mar 2006, Duncan Murdoch wrote:
> On 3/12/2006 6:39 PM, [hidden email] wrote:
> > Full_Name: Matthew Davis
> > Version: 2.2.0
> > OS: OS X (10.4.5)
> > Submission from: (NULL) (209.107.120.195)
> >
> >
> > the mean of my sample x is 0.2, and when I check mean(x)<=0.2 I get a TRUE
> > value, when I check mean(x)<=(10.8) I get a FALSE value. (x < c(0, 1, 0, 0,
> > 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0))
>
> Why make this so complicated? The natural conclusion from that is that
> 0.2 is not equal to (10.8), and indeed:
>
> > (10.8) == 0.2
> [1] FALSE
>
> The problem is that neither 0.2 nor 0.8 can be represented exactly, so
> when you do calculations using them you are doing approximations. The
> approximation involving your mean is different than the one involving
> (10.8). This is an FAQ,
>
> 7.31 Why doesn't R think these numbers are equal?
>
> This is not a bug.
>
> Duncan Murdoch
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/rdevel>
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On 3/12/2006 7:08 PM, Janusz Kawczak wrote:
> However, mean(x)==0.2 returns TRUE
> Also, mean(x)>=(10.8) returns TRUE ;)
>
> So, it's not just the approximation calculus.
I don't get your point. On my computer,
> 10.8 < 0.2
[1] TRUE
which is consistent with what I wrote below and what you write above.
mean(x) comes out to the same approximation as the constant 0.2 uses,
but 10.8 doesn't, it comes out smaller.
Duncan Murdoch
>
> On Sun, 12 Mar 2006, Duncan Murdoch wrote:
>
>> On 3/12/2006 6:39 PM, [hidden email] wrote:
>>> Full_Name: Matthew Davis
>>> Version: 2.2.0
>>> OS: OS X (10.4.5)
>>> Submission from: (NULL) (209.107.120.195)
>>>
>>>
>>> the mean of my sample x is 0.2, and when I check mean(x)<=0.2 I get a TRUE
>>> value, when I check mean(x)<=(10.8) I get a FALSE value. (x < c(0, 1, 0, 0,
>>> 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0))
>> Why make this so complicated? The natural conclusion from that is that
>> 0.2 is not equal to (10.8), and indeed:
>>
>> > (10.8) == 0.2
>> [1] FALSE
>>
>> The problem is that neither 0.2 nor 0.8 can be represented exactly, so
>> when you do calculations using them you are doing approximations. The
>> approximation involving your mean is different than the one involving
>> (10.8). This is an FAQ,
>>
>> 7.31 Why doesn't R think these numbers are equal?
>>
>> This is not a bug.
>>
>> Duncan Murdoch
>>
>> ______________________________________________
>> [hidden email] mailing list
>> https://stat.ethz.ch/mailman/listinfo/rdevel>>
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