I think there may 3 legends should be added in your plot
the argument col, pch and pt.cex should be in the same length with legend,
but the objects col, pch
and cex you defined former have 16*3 length. I guess the follow codes may
work
col <- rep(c("blue", "red", "darkgreen"), c(16, 16, 16))
## Choose different size of points
cex <- rep(c(1, 1.2, 1), c(16, 16, 16))
## Choose the form of the points (square, circle, triangle and
diamond-shaped
pch <- rep(c(15, 16, 17), c(16, 16, 16))
plot(axis1, axis2, main="My plot", xlab="Axis 1", ylab="Axis 2",
col=c(Category, col), pch=pch, cex=cex)
legend(4, 12.5, c("NorthAmerica", "SouthAmerica", "Asia"), col =
unique(col),
pch = unique(pch), pt.cex = unique(cex), title = "Region")
--
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