From: Jim Lemon <bitwrit@ozemail.com.au>
Organization: bitwrit software
To: Levivier Emilie <Emilie.Levivier@lmcp.jussieu.fr>,
        r-help@stat.math.ethz.ch
Subject: Re: [R] Plot problem !

Levivier Emilie wrote:

> Hello,
>
> Is there a simple way to make a plot with xy coordinates and a z value
> which determines the size and the color of point on the plot?

This is pretty basic, but may be helpful:

> test<-c(2,6,4,7,5,6,8,3,7,2)
> plot(test,type="n",main="Color/size test plot",ylab="Size scale",xlab="Color
scale")
> colsiz<-function (yvec) {
    ymin <- min(yvec)
    cexdiv <- max(yvec)/2
    for (i in 1:length(yvec)) {
        nextcex <- (yvec[i] - ymin)/cexdiv + 1
        par(cex = nextcex)
        points(i, yvec[i], type = "p", col = i)
    }
}
> colsiz(test)

Note that the size here ranges from 1->2.  You can change that by fiddling with
the calculation of 'cexdiv'.
Oops, I just realized that I used the x and y values to determine the color and
size, but that may be what you wanted anyway...

Jim