ggplot linetype causing line to be invisible

Question

I want to plot some lines and have them differentiated on color and linetype. If I differentiate on color alone, it's fine. If I add linetype, the line for group 14 vanishes.

(ggplot2_2.1.0, R version 3.3.1)

library(ggplot2)
g <- paste("Group", 1:14)
group <- factor(rep(g, each=14), levels=g)
x <- rep(1:14, length.out=14*14)
y <- c(runif(14*13), rep(0.55, 14))

d <- data.frame(group, x, y, stringsAsFactors=FALSE)

# Next 2 lines work fine - check the legend for Group 14
ggplot(d, aes(x, y, color=group)) +
  geom_line()

# Add linetype
ggplot(d, aes(x, y, color=group, linetype=group)) +
  geom_line()
# Group 14 is invisible!

What's going on?

I think you've exhausted the number of distinct line types in ggplot, and the default behavior at that point is to use 'blank' for the additional lines. See what happens if you increase the number of groups even further. — ulfelder
scale_linetype_manual(values=1:14) is the override I'm using and it works. If I increase the groups further, I get more blanks. Silently defaulting to blanks doesn't seem ideal. — harrys

cuttlefish44 cuttlefish44 · Accepted Answer · 2016-10-29T12:10:08

You can solve it by defining a form of each line manually with hex strings (see ?linetype).

?linetype

..., the string "33" specifies three units on followed by three off and "3313" specifies three units on followed by three off followed by one on and finally three off.

HEX <- c(1:9, letters[1:6])  # can't use 0 

 ## make linetype with (two- or) four‐digit number of hex
  # In this example, I made them randomly
set.seed(1); HEXs <- matrix(sample(HEX, 4*14, replace = T), ncol = 4)
my_val <- apply(HEXs, 1, function(x) paste0(x[1], x[2], x[3], x[4]))

 # example data
group <- factor(rep(paste("Group", 1:14), each = 20), levels=paste("Group", 1:14))
data <- data.frame(x = 1:20, y = rep(1:14, each=20), group = group)

ggplot(data, aes(x = x, y = y, colour = group, linetype = group)) +
  geom_line() +
  scale_linetype_manual(values = my_val)

ggplot linetype causing line to be invisible

1 Answers