negative and positive values in diff. colors

Hi

Hi R-users,

I have a set of elevation residuals as geodata points. I would like to
display them in the following way:
-negative values using pch=20 (filled circle)
-positive values using pch=1  (empty circle)

while using the cex.max=5, cex.min=0.1 for points() to represent the
residuals value. Basically I would like to distinguish neagtive and
positive values at my map. How to do this.

Do you mean something like this ... ?

x <- rnorm(50)
y <- rnorm(50)
z <- rnorm(50)
pch <- rep(1, 50)
pch[z < 0] <- 20
cex <- (abs(z)/max(abs(z))) * 4.9 + 0.1
plot(x, y, pch=pch, cex=cex)

Paul
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