删除ggplot中的图例标题

Question

I'm trying to remove the title of a legend in ggplot2 :

df <- data.frame(
  g = rep(letters[1:2], 5),
  x = rnorm(10),
  y = rnorm(10)
)

library(ggplot2)
ggplot(df, aes(x, y, colour=g)) +
  geom_line(stat="identity") + 
  theme(legend.position="bottom")

I've seen this question and none of the solutions there seem to work for me. Most give an error about how opts is deprecated and to use theme instead. I've also tried various versions of theme(legend.title=NULL) , theme(legend.title="") , theme(legend.title=element_blank) , etc. Typical error messages are:

'opts' is deprecated. Use 'theme' instead. (Deprecated; last used in version 0.9.1)
'theme_blank' is deprecated. Use 'element_blank' instead. (Deprecated; last used in version 0.9.1)

I'm using ggplot2 for the first time since version 0.9.3 was released and I'm finding it difficult to navigate some of the changes...

Answer 1

You were almost there : just add theme(legend.title=element_blank())

ggplot(df, aes(x, y, colour=g)) +
  geom_line(stat="identity") + 
  theme(legend.position="bottom") +
  theme(legend.title=element_blank())

This page on Cookbook for R gives plenty of details on how to customize legends.

Answer 2

This works too and also demonstrates how to change the legend title:

ggplot(df, aes(x, y, colour=g)) +
  geom_line(stat="identity") + 
  theme(legend.position="bottom") +
  scale_color_discrete(name="")

Answer 3

Another option using labs and setting colour to NULL .

ggplot(df, aes(x, y, colour = g)) +
  geom_line(stat = "identity") +
  theme(legend.position = "bottom") +
  labs(colour = NULL)

Answer 4

Since you may have more than one legends in a plot, a way to selectively remove just one of the titles without leaving an empty space is to set the name argument of the scale_ function to NULL , ie

scale_fill_discrete(name = NULL)

(kudos to @pascal for a comment on another thread )

Answer 5

For Error: 'opts' is deprecated . Use theme() instead. (Defunct; last used in version 0.9.1)' I replaced opts(title = "Boxplot - Candidate's Tweet Scores") with labs(title = "Boxplot - Candidate's Tweet Scores") . It worked!