[R] Boxplot philosophy {was "Boxplot in R"}
(Ted Harding)
Ted.Harding at nessie.mcc.ac.uk
Tue Jul 12 11:27:17 CEST 2005
On 12-Jul-05 Ted Harding wrote:
> On 12-Jul-05 Spencer Graves wrote:
>> I'll bite: How does one detect bimodalidty from a boxplot?
>>
>> spencer graves
>>
>> Berton Gunter wrote:
>> [...]
>>> Finally, a tidbit for boxplot afficianados: how does one detect
>>> bimodality from a boxplot?
>>>
>>> -- Bert Gunter
>
> Not definitively detectable of course, but certainly suspectable.
>
> Hint: What is the relationship between the distances from the "median"
> line to the extremes of the "box", and from the extremes of the "box"
> to the ends of the "whiskers", in the case of a uniform distribution?
>
>
>
> If that doesn't trigger it, then:
>
> Hint:
>
> unimod<-rnorm(1000,0,sqrt(26))
> nomod<-sqrt(12*26)*runif(1000)
> boxplot(data.frame(cbind(unimod,nomod,bimod)))
OOPS!! (cut-&-pasted the wrong lines):
unimod<-rnorm(1000,0,sqrt(26))
nomod<-sqrt(12*26)*(runif(1000)-0.5)
bimod<-c(rnorm(500,-5,1),rnorm(500,5,1))
boxplot(data.frame(cbind(unimod,nomod,bimod)))
> Best wishes,
> Ted.
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Date: 12-Jul-05 Time: 10:24:34
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