[R] Is there a regression surface demo?

[Joshua Wiley]

Thanks for everyone's responses. Just to follow up, here is a working
version of my original.  The code is not pretty, but it functions.
Assuming you have the 'rgl' package installed and have sourced this
function, here are some examples:

RegSurfaceDemo(mpg ~ vs + wt, data = mtcars)
RegSurfaceDemo(mpg ~ vs * wt, data = mtcars)
RegSurfaceDemo(qsec ~ disp * hp, data = mtcars)

It cannot handle factors, and the axes labels are hideous...I'll get
to that eventually.

Thanks for all your help and suggestions.

Josh

RegSurfaceDemo <- function(formula, data, xlim = NULL, ylim = NULL,
                           zlim = NULL, resolution = 10) {
 require(rgl)
 ## This cannot be the proper way to extract variable names from formula
 vars <- rownames(attr(terms(formula), "factors"))

 ## if no limits set, make them nearest integer to
 ## .75 the lowest value and 1.25 the highest
 ranger <- function(x) {
   as.integer(range(x) * c(.75, 1.25))
 }
 if(is.null(xlim)) {xlim <- ranger(data[, vars[2]])}
 if(is.null(ylim)) {ylim <- ranger(data[, vars[3]])}
 if(is.null(zlim)) {zlim <- ranger(data[, vars[1]])}

 ## This does not actually work because the data frame
 ## does not get named properly (actually it throws an error)
 f <- function (x, y) {
   newdat <- data.frame(x, y)
   colnames(newdat) <- c(vars[2], vars[3])
   predict(my.model, newdata = newdat)
 }

 ## Fit model
 my.model <- lm(formula = formula, data = data)

 ## Create X, Y, and Z grids
 X <- seq(from = xlim[1], to = xlim[2], length.out = resolution)
 Y <- seq(from = ylim[1], to = ylim[2], length.out = resolution)
 Z <- outer(X, Y, f)

 ## Create 3d scatter plot and add the regression surface
 open3d()
 with(data = data,
      plot3d(x = get(vars[2]), y = get(vars[3]), z = get(vars[1]),
             xlim = xlim, ylim = ylim, zlim = zlim))
 par3d(ignoreExtent = TRUE)
 surface3d(X, Y, Z, col = "blue", alpha = .6)
 par3d(ignoreExtent = FALSE)
 return(summary(my.model))
}



On Mon, Oct 11, 2010 at 1:28 PM, Ista Zahn <izahn at psych.rochester.edu> wrote:
> There is also wireframe() in lattice and bplot in rms.
>
> -Ista
>
> On Mon, Oct 11, 2010 at 3:49 PM, G. Jay Kerns <gkerns at ysu.edu> wrote:
>> Dear Josh,
>>
>> On Mon, Oct 11, 2010 at 3:15 PM, Joshua Wiley <jwiley.psych at gmail.com> wrote:
>>> Hi All,
>>>
>>> Does anyone know of a function to plot a regression surface for two
>>> predictors?  RSiteSearch()s and findFn()s have not turned up what I
>>> was looking for.  I was thinking something along the lines of:
>>> http://mallit.fr.umn.edu/fr5218/reg_refresh/images/fig9.gif
>>>
>>> I like the rgl package because showing it from different angles is
>>> nice for demonstrations.  I started to write my own, but it has some
>>> issues (non functioning code start below), and I figured before I
>>> tried to work out the kinks, I would ask for the list's feedback.
>>>
>>> Any comments or suggestions (about functions or preferred idioms for
>>> what I tried below, or...) are greatly appreciated.
>>>
>>> Josh
>>>
>>
>> [snip]
>>
>> I haven't tried to debug your code, but wanted to mention that the
>> Rcmdr:::scatter3d function does 3-d scatterplots (with the rgl
>> package) and adds a regression surface, one of 4 or 5 different types.
>>  If nothing else, it might be a good place to start for making your
>> own.
>>
>> A person can play around with the different types in the Rcmdr under
>> the Graphs menu.  Or, from the command line:
>>
>> library(Rcmdr)
>> with(rock, scatter3d(area, peri, shape))
>>
>> I hope that this helps,
>> Jay
>>
>> ______________________________________________
>> 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.
>>
>
>
>
> --
> Ista Zahn
> Graduate student
> University of Rochester
> Department of Clinical and Social Psychology
> http://yourpsyche.org
>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/