Three suggestions:
# for 2 plotting symbols
set.seed(12)
head(dat <- data.frame(X=rnorm(20), Y=rnorm(20),
PCH=sample(letters[1:2], 20, replace=TRUE))) #
2 plotting symbols
with(dat, plot(X, Y, pch=ifelse(PCH=="a", 1, 20)))
# for n plotting symbols, simpler
set.seed(12)
head(dat <- data.frame(X=rnorm(20), Y=rnorm(20),
PCH=sample(letters[1:5], 20, replace=TRUE)))
with(dat, plot(X, Y, pch=as.numeric(PCH)))
# and of course as.numeric(PCH) could be used with subsetting
# for n plotting symbols, more customizable
with(dat, plot(X, Y, pch=c(20, 18, 16, 1, 10)[as.numeric(PCH)]))
Best,
STG
--
Stefan Th. Gries
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Univ. of California, Santa Barbara
http://tinyurl.com/stgries
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