Hello,

I plot box plot, and add a point to the box indicating mean. I also add some
range to the box width. I want to add legend for both the range (line) and
mean (point). However, I cannot add line legend and point legend together.
The code looks like the following.

(1) First, I tried the following code, however, it plot a line across the
point legend("*").

boxplot(count ~ spray, data = InsectSprays)

rb <- boxplot(decrease ~ treatment, data = OrchardSprays, col="lightgrey")
title("Comparing boxplot()s and non-robust mean +/- SD")

mn.t <- tapply(OrchardSprays$decrease, OrchardSprays$treatment, mean)
xi <- seq(rb$n)
points(xi, mn.t, col = "blue", pch = "*")

h1 <- abline(h=110, col="red")
h2 <- abline(h=0, col="red", lty="dotted")

legend("topleft", c("110", "0", "mean"),
        lty = c("solid","dotted"), pch = c(" ", " ", "*"),
        col = c("red","red", "blue"),lwd = c(1,1))



(2) I then tried the following

legend("topleft", c("110", "0", "mean"),
        lty = c("solid","dotted"," "), pch = c(" ", " ", "*"),
        col = c("red","red", "blue"),lwd = c(1,1))


It returns error as lty cannot be " ".

Error in segments(x1, y1, x2, y2, ...) : invalid line type: must be length
2, 4, 6 or 8


Can anyone help me out? Thank you.

Shiguo

-- 
Department of Geography
The Ohio State University
1036 Derby Hall
154 N Oval Mall
Columbus, OH 43210
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