g <- symbolmap(range=c(-1,1),
shape=function(x) ifelse(x > 0, "circles", "squares"),
size=function(x) sqrt(ifelse(x > 0, x/pi, -x))/15,
bg=function(x) ifelse(x > 0, "green", "red"))
plot(square(1), main="")
a <- invoke.symbolmap(g, runif(10, -1, 1), runifpoint(10), add=TRUE)
a
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