如何在 ggplot 中更改传奇标题

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?

This should work:

p <- ggplot(df, aes(x=rating, fill=cond)) + 
           geom_density(alpha=.3) + 
           xlab("NEW RATING TITLE") + 
           ylab("NEW DENSITY TITLE")
p <- p + guides(fill=guide_legend(title="New Legend Title"))

(or alternatively)

p + scale_fill_discrete(name = "New Legend Title")

Since you have two densitys I imagine you may be wanting to set your own colours with scale_fill_manual.

If so you can do:

df <- data.frame(x=1:10,group=c(rep("a",5),rep("b",5)))

legend_title <- "OMG My Title"

ggplot(df, aes(x=x, fill=group)) + geom_density(alpha=.3) +   
    scale_fill_manual(legend_title,values=c("orange","red"))

There's another very simple answer which can work for some simple graphs.

Just add a call to guide_legend() into your graph.

ggplot(...) + ... + guide_legend(title="my awesome title")

As shown in the very nice ggplot docs.

If that doesn't work, you can more precisely set your guide parameters with a call to guides:

ggplot(...) + ... + guides(fill=guide_legend("my awesome title"))

You can also vary the shape/color/size by specifying these parameters for your call to guides as well.

I didn't dig in much into this but because you used fill=cond in ggplot(),

 + labs(color='NEW LEGEND TITLE') 

might not have worked. However it you replace color by fill, it works!

+ labs(fill='NEW LEGEND TITLE') 

This worked for me in ggplot2_2.1.0

P.S. I would have commented but my stackoverflow reputation is not enough to comment.

Since in your code you used ggplot(data, fill= cond) to create the histogram you need to add the legend title by also using "fill" in the label section i.e. +labs(fill="Title name"). If you were using a different type of plot where the code was ggplot(data, colour= cond), then you could use +labs(colour= "Title Name"). In summary, the lab argument has to match the aes argument.

I have used + guides(fill=guide_legend("my awesome title")) to change the legend title on geom_bar plots but it did not seem to work for geom_point.

I am using a facet_wrap in my ggplot and none of the suggested solutions worked for me except ArnaudA's solution:

qplot(…) + guides(color=guide_legend(title="sale year")) 

You can also add a single line (last line):

ggplot(df, aes(x=rating, fill=cond)) + 
  geom_density(alpha = .3) +
  xlab("NEW RATING TITLE") +
  ylab("NEW DENSITY TITLE") +
  labs(fill = "Your Title")

None of the above code worked for me.

Here's what I found and it worked.

labs(color = "sale year")

You can also give a space between the title and the display by adding \n at the end.

labs(color = 'sale year\n")