Hi Wayne,

I have two suggestion to you.
1. You add some random noise on both x and y data or
2. You graph bubble points, where the size is proportional to the frequence of the xy combination.

x<-sample(1:10,10000,replace=T)
y<-sample(1:10,10000,replace=T)
xy<-cbind(x,y)
x11(1400,800)
par(mfrow=c(1,3))
plot(xy)
xy.random<-xy+rnorm(20000,0.1,0.1) 
plot(xy.random,cex=0.1)
xy.tab<-data.frame(table(x,y))
xy.tab$x<-as.numeric(as.character(xy.tab$x))
xy.tab$y<-as.numeric(as.character(xy.tab$y))
min.freq<-min(xy.tab$Freq)
max.freq<-max(xy.tab$Freq)
plot(xy.tab$x,xy.tab$y,cex=(xy.tab$Freq-min.freq)/(max.freq-min.freq)*5)

Kind regards,

Miltinho
Brazil


----- Mensagem original ----
De: Wayne Aldo Gavioli <wgavioli@fas.harvard.edu>
Para: r-help@r-project.org
Enviadas: Segunda-feira, 17 de Dezembro de 2007 22:14:23
Assunto: [R] Scatterplot Showing All Points



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"?


Thanks,


Wayne

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