[R] Scatterplot Showing All Points

[Jim Lemon]

Wayne Aldo Gavioli wrote:
> 
> Hello all,
> 
> 
> I'm trying to graph a scatterplot of a large (5,000 x,y coordinates) of data
> with the caveat that many of the data points overlap with each other (share the
> same x AND y coordinates).  In using the usual "plot" command,
> 
> 
> 
>>plot(education, xlab="etc", ylab="etc")
> 
> 
> 
> it seems that the overlap of points is not shown in the graph.  Namely, there
> are 5,000 points that should be plotted, as I mentioned above, but because so
> many of the points overlap with each other exactly, only about 50-60 points are
> actually plotted on the graph.  Thus, there's no indication that Point A shares
> its coordinates with 200 other pieces of data and thus is very common while
> Point B doesn't share its coordinates with any other pieces of data and thus
> isn't common at all.  Is there anyway to indicate the frequency of such points
> on such a graph?  Should I be using a different command than "plot"?
> 
Hi Wayne,
While this is not a really pretty picture, you can get a viewable plot 
with count.overplot if the first two elements of "education" are named 
"x" and "y" and they are the coordinates you want to plot. Otherwise, 
pass the x and y coordinates separately.

library(plotrix)
count.overplot(education,
  tol=c(diff(range(education$x))/10,
  diff(range(education$y))/10))

Jim