[R] Scatterplot3d model reporting question

[John Fox]

Dear Max,

I'm guessing that you're actually using scatter3d() in the Rcmdr package rather than scatterplot3d(), since the latter, I believe, doesn't fit regression surfaces.

If I'm right, then as it says in ?scatter3d, the smooth surface is fit by the gam() function in the mgcv package using a smoothing spline and there is no explicit equation to examine. See ?gam for more information.

I hope this helps,
 John

--------------------------------
John Fox, Professor
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Max
> Sent: December-18-07 2:02 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Scatterplot3d model reporting question
> 
> I've used the scatterplot3d function to graph some data and had it
> graph a "smooth" fit. Is there a way to actualy find out the function
> of the surface? I've looked through the help and figured out how to get
> it to report the following:
> 
> Family: gaussian
> Link function: identity
> 
> Formula:
> y ~ s(x, z)
> 
> Parametric coefficients:
>             Estimate Std. Error t value Pr(>|t|)
> (Intercept)  0.20750    0.01223   16.97   <2e-16 ***
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> 
> Approximate significance of smooth terms:
>          edf Est.rank     F  p-value
> s(x,z) 8.403       17 9.729 1.76e-14 ***
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> 
> R-sq.(adj) =  0.684   Deviance explained = 70.9%
> GCV score = 0.017692   Scale est. = 0.016151  n = 108
> 
> But I'm still not really sure what I'm looking at, either that or
> "smooth" means something different than I thought. Any help would be
> great!
> 
> thanks,
> 
> -Max
> 
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