[R] density plot on a log scale

[Jim Lemon]

On 06/14/2012 07:08 PM, field.cady wrote:
> I'm working with a large dataset - large enough that when I do a scatter plot
> the points all blur together, so I want to plot their density by color - a
> heat map or something like that.  I've used smoothScatter for tasks like
> this, but the problem is that my current dataset really only looks good on a
> log-log scale.  When I do the following command
>
> smoothScatter(
>          data,
>          xlim=c(100,100000000),
>          ylim=c(100,10000000000),
>          log="xy",
>          pch="."
> )
>
> the output seems to only show a few of the points, and they are in odd
> places that don't seem to correlate at all with the colors.  I got a warning
> that I should increase the gridsize, but even using comically large values
> (nbin=10000) didn't help.  Does anybody know how I can do this?  Thanks!
>
Hi field.cady,
This is a very rough example (I haven't bothered to do the log 
transformation or anything and the matrix is upside down), but it might 
get you where you want to go.

x<-runif(1000)
y<-runif(1000)
xydens<-matrix(0,10,10)
xybreaks<-seq(0,1,length.out=11)
for(row in 1:10) {
  for(column in 1:10)
   xydens[row,column]<-
   sum(x>=xybreaks[row] & x < xybreaks[row+1] &
   y >= xybreaks[column] & y < xybreaks[column+1])
}
library(plotrix)
color2D.matplot(xydens)

Jim