[R] scatterplot of 100000 points and pdf file format

[Barry Rowlingson]

> 
> I would strongly suggest a different method to present the data such as a 
> contour plot or 3D bar plot.  An XY plot with a million points is unlikely to 
> be readable unless it is produced as a large format print.  At 200 DPI 
> printed, 1,000,000 discrete points requires a minimum of a 5 inch (12.7          
> cm) by 5 inch area.  Besides, other than being visually overwhelming, what 
> information would such a plot offer a viewer?

  I recall some of our extreme value statistics people printing things 
like this. Several million points on a plot. Most of which were in a 
big, thick block of toner, and then a few hundred at the extremes which 
was where they where interested in looking.

  Of course these things took an hour to print on a PostScript printer 
at the time. I think I suggested only plotting points for which X > 
someThreshold. Saved on toner and time. Got a bit tricky in the 
bivariate case though, where you really needed to plot points outside 
some ellipse that you knew would otherwise be a big black blob, and then 
you filled that in with a black ellipse.

  Contours or aggregation wasn't any use, since they were interested in 
the point patterns of the extreme value data.

Baz