On Sep 30, 2011, at 10:14 AM, Duncan Murdoch wrote:
On 30/09/2011 10:00 AM, David Winsemius wrote:
On Sep 30, 2011, at 4:50 AM, sreblam wrote:
> Hi!
> I'm trying to implement in R in an easy way the negative
reflection
> method
> described in Silverman (1986) on p.31, ie I have a non-negative
> dataset and
> would like to estimate the density by applying a reflection method
> where the
> reflected points have weight -1.
> I thought there should be a way to evaluate the wanted kernel at
the
> required points, in other words to calculate formula (2.16):
> fhat(x) = 1/(nh) * sum_{i=1}^{n}{ K( (x-Xi) /h) - K( (x-Xi) /h) }
>
> Unfortunately, I am still not that good and skilled with R - does
> anybody
> know how to do this- Or maybe a hint...?
> Thank you!!
Doing what I thought was the obvious search ( "negative reflection
density" ) done at the obvious search site (the one to which
RSiteSearch("negative reflection density") ) typed at the console
would have taken you) and twiddling with the setting produces this
perfect match as its second hit:
http://finzi.psych.upenn.edu/Rhelp10/2010-July/246526.html
That's a reflection density estimate, but not a "negative
reflection" estimate. The latter aims for zero density at location
0, not zero gradient to the density there.
Thanks for the correction, Duncan. Didn't you think the code that Ravi
presented could be converted to that purpose with the simple addition
of a minus sign?
--
David.
Duncan Murdoch
Now it is true that you wouldn't have gotten that with the console
entered string which is why I created a new function (and a new
browser button that fiddles with the default setting for RSiteSearch:
rhelpSearch<- function(string,
restrict = c("Rhelp10", "Rhelp08", "Rhelp02",
"functions" ),
matchesPerPage = 100, ...)
RSiteSearch(string=string, restrict = restrict,
matchesPerPage = matchesPerPage, ...)
R-search button mapped to:
http://search.r-project.org/cgi-bin/namazu.cgi?query=&max=100&result=normal&sort=score&idxname=Rhelp10&idxname=Rhelp08&idxname=Rhelp02&idxname=functions
>
> PS: you can also find the mentioned passage on p.21 of
> http://ned.ipac.caltech.edu/level5/March02/Silverman/paper.pdf
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Implementing-Silverman-s-Negative-Reflection-tp3859191p3859191.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@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.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@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.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@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.
