[R] length of a density curve (or any curve)

[sylvain willart]

Thanks for your answer,

@Dennis Murphy: no, I don't know the functionnal form, this is purely
empirical data

@ Ted Harding: Thank you for your lines of code, they are actually a
pretty smart way...

SW

2009/12/4 Ted Harding <Ted.Harding at manchester.ac.uk>:
> True enough -- ?density does not address the issue of computing
> the length pf the curve!
>
> One simple way of implementing the idea you first thought of
> would be on the following lines:
>
>  d <- density(MyData$x)
>  sum(sqrt(diff(d$x)^2 + diff(d$y)^2))
>
> which simply sums the lengths of the line-segments. You would
> get a better approximation to the ideal length by increasing
> the value of 'n' in the call to density() (perhaps as a separate
> calculation, since a relatively small value of 'n' is likely
> to be adeqaute for plotting, but possibly inadequate for the
> accurate computation of the length).
>
> Hpoing this helps,
> Ted.
>
> On 04-Dec-09 12:41:22, sylvain willart wrote:
>> Yes, sure (and I just did it again)
>> but I can't see an answer... did I miss sthg ?
>>
>> regards,
>>
>> SW
>>
>> 2009/12/4 milton ruser <milton.ruser at gmail.com>:
>>> hi Sylvain,
>>>
>>> did you try ?density
>>>
>>> regards
>>>
>>> milton
>>>
>>> On Fri, Dec 4, 2009 at 7:19 AM, sylvain willart
>>> <sylvain.willart at gmail.com>
>>> wrote:
>>>>
>>>> Hello R users,
>>>>
>>>> When I type
>>>>
>>>> d <- density(MyData$x)
>>>>
>>>> I obtain a density object I can plot,
>>>>
>>>> But I wonder if there is a way to easily compute the length of the
>>>> density curve ?
>>>>
>>>> ( I imagine I could compute the distances between the 512 equally
>>>> spaced points using their x and y, but does it exist a smarter way ?)
>>>>
>>>> Regards,
>>>>
>>>> SW
>>>>
>>>> ______________________________________________
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>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>>
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
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> Date: 04-Dec-09                                       Time: 13:02:27
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