How to change legend title in ggplot

Question

I have the following plot like below. It was created with this command:

library(ggplot2)

df <- data.frame(cond = factor(rep(c("A", "B"), each = 200)), 

                 rating = c(rnorm(200), rnorm(200, mean=.8)))

ggplot(df, aes(x=rating, fill=cond)) + 

geom_density(alpha = .3) +

xlab("NEW RATING TITLE") +

ylab("NEW DENSITY TITLE")

Now next thing I want to do is to modify the legend title from cond into NEW LEGEND TITLE.

So what I did is to just add the following line add the end of the above code:

+labs(colour="NEW LEGEND TITLE")

But it doesn't work. What's the right way to do it?

Answer 1

To change the legend title of your plot, add the following layer:

labs(fill = "New Legend Title") 

i.e.,

ggplot(df, aes(x=rating, fill=cond)) +

  geom_density(alpha = .3) +

  xlab("NEW RATING TITLE") +

  ylab("NEW DENSITY TITLE")+

  labs(fill = "NEW LEGEND TITLE")

Output:

Answer 2

I think your approach isn't working because you have used fill=cond in ggplot():

 + labs(color='NEW LEGEND TITLE') 

However, if you replace color by fill, it will work finely:

+ labs(fill='NEW LEGEND TITLE')