[R] rewrite of scatter.smooth to handle NAs

[Berton Gunter]

Lazy evaluation. See V&R's S Programming for a good explanation. But, in
brief, the default values for xlab and ylab are not evaluated until they are
needed. If plot(..., xlab=...) appears after the assignments to x and y,
then x and y are no longer the original argument expressions but numeric
vectors.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of William Briggs
> Sent: Thursday, February 10, 2005 1:29 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] rewrite of scatter.smooth to handle NAs
> 
> 
> I rewrote scatter.smooth to handle missing values, but I have 
> a question 
> about a move I had to make.  Here's the code:
> 
> Mscatter.smooth<-function (x, y, span = 2/3, degree = 1, family = 
> c("symmetric",
>      "gaussian"), xlab = deparse(substitute(x)), ylab = 
> deparse(substitute(y)),
>      ylim = range(y, prediction$y), evaluation = 50, ...)
> {
>      if (inherits(x, "formula")) {
>          if (length(x) < 3)
>              stop("need response in formula")
>          thiscall <- match.call()
>          thiscall$x <- x[[3]]
>          thiscall$y <- x[[2]]
>          return(invisible(eval(thiscall, sys.parent())))
>      }
> ##################
>      plot(x, y, xlab = xlab, ylab = ylab, ...)
> 	i<-complete.cases(x,y)
> 	x<-x[i]
> 	y<-y[i]
> ##################
>      prediction <- loess.smooth(x, y, span, degree, family, 
> evaluation)
>      lines(prediction)
>      invisible()
> }
> 
> The changes I made are between the '###########'.  The idea 
> was only to 
> pass complete cases on to loess.smooth and thus avoice the NA error 
> you'd usually get by calling scatter.smooth with missing values.
> 
> I had to move the plot above the loess.smooth, whereas in the orginal 
> scatter.smooth is was just below to take adavantage of 
> prediction$y to 
> set the ylim in the plotting function.
> 
> But if I try to plot after creating the complete cases, the 
> names of the 
> x and y variables disappear and instead the plotting labels 
> on the x and 
> y axis look like, for example, 'c(1,2,1.2,5.2, ...)', that is, the 
> vector of values being plotted.
> 
> Why does that happen?
> 
> Matt
> -- 
> William (Matt) Briggs
> Assistant Professor of Biostatistics
> Division of General Internal Medicine
> Weill Medical College of Cornell University
> 525 East 68th St., Box #46
> New York, NY 10021
> Tel: 212-628-0128; Fax: 212-746-8965
> 
> http://drclamp.wmbriggs.com
> 
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