ggplot2在图例中显示的线型不正确

Question

I'm following this links example , as I have a similar situation where I'm trying to graph two data frames in the same plot. I'm only interested in changing the linetypes for one of the data frames, which works in the graph, but doesn't display correctly in the legend.

Example dataset:

set.seed(456)
n <- 20
dfr <- data.frame(
  id=rep(1:n, 2),
  group=rep(c("1","2"), each=n), value=c(rnorm(n), rnorm(n, sd=1.1))
)

df_95ci <- data.frame(y_values=c(-1,1)*qnorm(0.95)) 
df_99ci <- data.frame(y_values=c(-1,1)*qnorm(0.99))

require(ggplot2)

Code:

  ggplot(data=dfr, mapping=aes(x=id, y=value)) +
  geom_line(mapping=aes(colour=group)) +
  geom_hline(data= df_95ci, mapping=aes(yintercept=y_values, size= "95% CI"), colour = "orange", linetype="dotdash") +
  geom_hline(data= df_99ci, mapping=aes(yintercept=y_values, size= "99% CI"), colour = "darkred", linetype="dotted") +
  scale_color_hue("Group") +
  scale_size_manual(
    "CI horizontal line", values=rep(1,4),
    guide=guide_legend(override.aes = list(colour=c("orange", "darkred")))
  ) +
  scale_linetype_identity(guide="legend")

Output

As you can see I have two lines with different linetypes, but they're identical in the legend.

Answer 1

Do you want this?

ggplot(data=dfr, mapping=aes(x=id, y=value)) +
    geom_line(mapping=aes(colour=group)) +
    geom_hline(data= df_95ci, mapping=aes(yintercept=y_values, linetype= "95% CI"), 
               colour = "orange", size = 1) +
    geom_hline(data= df_99ci, mapping=aes(yintercept=y_values, linetype= "99% CI"), 
               colour = "darkred", size = 1) +
    scale_linetype_manual(
        "CI horizontal line", values=c("95% CI" = 4, "99% CI" = 3),
        guide=guide_legend(override.aes = list(colour=c("orange", "darkred")))
    )