Re: [R] Smoothing z-values according to their x, y positions

From: David Winsemius <dwinsemius_at_comcast.net>
Date: Thu, 20 Mar 2008 01:40:17 +0000 (UTC)

"Emmanuel Levy" <emmanuel.levy_at_gmail.com> wrote in news:e4654710803191554k4dfc2728g70bde35f41627754_at_mail.gmail.com:

> Dear Bert,
>
> Thanks for your reply - I indeed saw a lot of functions using:
> help.search("smooth")
>
> The problem is that most seem to not be very appropriate to what I'd
> like, or they seem extremely complicated (e.g. gma). I am probably
> missing something as I don't
> see how to use Loess. From my poor understanding, it seems to be for
> 2D data. Here I want to smooth the third "z" component.
>
> In the meantime I adapted a function from Greg Warnes, which sort of
> does the job (although the smoothing is not very nice).
> So I'd be very happy to learn how do do something similar with
> loess!
>

You could consider at combining the kde2d() function in the MASS package within the VR bundle in combination with contour(). The example I followed came from MASS 2ed in chapter 5's section on density estimation. It is probably easiest to just copy the help example:

library(MASS)
attach(geyser)
f1 <- kde2d(duration[-272], duration[-1],

             h = rep(1.5, 2), n = 50, lims = c(0.5, 6, 0.5, 6)) contour(f1, xlab = "previous duration",

        ylab = "duration", levels = c(0.05, 0.1, 0.2, 0.4) )

I have also had success with Loader's locfit package.

-- 
David Winsemius

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Received on Thu 20 Mar 2008 - 01:45:18 GMT

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