[R] Implementing Silverman's Negative Reflection

[Duncan Murdoch]

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.

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 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.
>
> David Winsemius, MD
> West Hartford, CT
>
> ______________________________________________
> 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.