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

[(Ted Harding)]

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
>>>
>>> ______________________________________________
>>> 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.
>>
>>
> 
> ______________________________________________
> 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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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 04-Dec-09                                       Time: 13:02:27
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