Thank you very much Peter,

I'm going to dig deeper into the code of the functions you've listed.


On Wed, Aug 3, 2011 at 6:57 AM, Peter Ehlers <ehlers@ucalgary.ca> wrote:

> On 2011-08-02 11:51, Sébastien Bihorel wrote:
>
>> Hi,
>>
>> This might be a simple problem but I don't know how to calculate a random
>> variable density the way panel.histogram does it before it creates the
>> actual density rectangles. The documentation says that it uses the density
>> function but the actual code suggests that the hist.constructor function
>> (which does not seem to be easily accessible).
>>
>
> The documentation in ?histogram is misleading. I think that the intent
> is that density() is used in panel.densityplot but panel.histogram uses
> hist(), as is clear in ?panel.histogram.
>
> So you'll find the code for the density rectangles in hist.default
> where 'counts' is computed and followed with
>
>  dens <- counts/(n * diff(breaks))
>
> You might find the code for truehist() in the MASS package easy to
> follow.
>
> To see how hist.constructor calls hist():
>
>  lattice:::hist.constructor
>
> Peter Ehlers
>
>
>> Any suggestion for computing the density values of foo$x in the following
>> example will be welcome.
>>
>>
>> require(lattice)
>> set.seed(12345)
>>
>> foo1<-
>> data.frame(x=rnorm(100,0,0.1),**grp=1,by=rep(1:2,each=50),by2=**
>> rep(1:2,times=50))
>> foo2<-
>> data.frame(x=rnorm(100,2,1),**grp=2,by=rep(1:2,each=50),by2=**
>> rep(1:2,times=50))
>> foo<- rbind(foo1,foo2)
>>
>> xplot<- histogram(~x,data=foo, type='density')
>>
>>
>> PS: the present question relates to a workaround for another problem
>> previously submitted to the list (
>> https://stat.ethz.ch/**pipermail/r-help/attachments/**
>> 20110727/5f0a8853/attachment.**pl<https://stat.ethz.ch/pipermail/r-help/attachments/20110727/5f0a8853/attachment.pl>
>> ).
>>
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>>
>
>

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