[R] Why does smoothScatter clip when xlim and ylim increased?

Duncan Murdoch murdoch at stats.uwo.ca
Sat Feb 6 14:15:43 CET 2010

On 06/02/2010 7:51 AM, Jennifer Lyon wrote:
 > Hi:
 > Is there a way to get smoothScatter to not clip when I increase the 
xlim and
 > ylim parameters?
 > Consider the following example:
 > set.seed(17)
 > x1<-rnorm(100)
 > x2<-rnorm(100)
 > smoothScatter(x1,x2)
 > #Now if I increase xlim and ylim notice that the plot seems to be 
clipped at
 > the former xlim, and ylim boundaries:
 > smoothScatter(x1,x2, xlim=c(-5,5), ylim=c(-5,5))

If you follow the links on the help page, you'll see that smoothScatter 
uses bkde2D, which has a range.x argument to control the range of the 
smoothing.  The smoothScatter function never passes the xlim and ylim 
values to bkde2D, only to the plotting functions, presumably because the 
author expected you to use them to limit the range, not extend it.

You can get the behaviour you want with specified xlim and ylim by 
modifying one line in smoothScatter:

map <- grDevices:::.smoothScatterCalcDensity(x, nbin, bandwidth)

should become

map <- grDevices:::.smoothScatterCalcDensity(x, nbin, bandwidth, 
list(xlim, ylim))

(You can use fix(smoothScatter) to edit your own local copy of 
smoothScatter and make this change.)

However, this messes up the default plot, so a better patch would be 
needed to permanently fix this.

Duncan Murdoch

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