How to Manually Change the Key Labels in a Legend in Ggplot2

How can I change legend labels in ggplot?

You can do that via the labels= argument in a scale_color_*() function by supplying a named vector. Here's an example:

library(ggplot2)

set.seed(1235)
df <- data.frame(x=1:10, y=1:10, z = sample(c("Control", "B", "C"), size=10, replace=TRUE))

df$z <- factor(df$z, levels=c("Control", "B", "C"))  # setting level order

p <- ggplot(df, aes(x,y, color=z)) + geom_point(size=4)
p

To change the name of "Control" totally "in plot code", I'll use scale_color_hue(labels=...). Note that by default, ggplot2 uses an evenly-spaced hue scaling, so this keeps the colors themselves the same. Using a named vector is not required, but a good idea to ensure you don't have mixing up of names/labels:

p + scale_color_hue(labels=c("Control" = "A", "B"="B", "C"="C"))

How to change legend title in ggplot

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")

How I do manually change the key labels values in a legend in ggplot2?

Thanks for you help Slowlearner. I just fixed the code with your commentaries. I could fix the code using melt() function at the beginning and scale_linetype_maunual into the code. Here is the new code.

library(reshape)

intactos2 <- melt(intactos, id.var = c("ecd","ACTIVIDAD"))

a <- ggplot(intactos2,aes(y = value,  x= ecd,group=ACTIVIDAD))+  
     geom_line(aes(colour = ACTIVIDAD,linetype=ACTIVIDAD),colour='black',size=0.5)+
     scale_linetype_manual("Glaciares rocosos",
                            breaks=c("1","2"), 
                            values=c("solid","dashed"),
                            labels = c("Activos", "Inactivos"))+
     ylab("Altitud m") +
     xlab("Distribucion Acumulada (%)\n")+
     scale_y_continuous(limits=c(3500,5000),
                        breaks=c(3500,3750,4000,4250,4500,4750,5000))+
     scale_x_continuous(limits = c(0.00, 1.00),
                        breaks = seq(0, 1, 0.1),
                        labels=seq(0,100,10))+
  theme(  plot.background  = element_rect(fill="white")
         ,panel.background = element_rect(fill='white')
         ,panel.grid.major = element_line(colour = 'grey', linetype = 'dotted',size=0.5)
         ,panel.grid.minor = element_line(colour = 'white', linetype = 'dashed')
         ,panel.border = element_blank()
         ,axis.line = element_line(colour = 'black')
         ,axis.text.x=element_text(colour="black")
         ,axis.text.y=element_text(colour="black")
         ,panel.grid.major =element_line(colour = 'grey', linetype = 'dashed')
         ,legend.key=element_rect(fill="white",colour="white"),legend.position=c(0.3,0.8))+
          geom_hline(aes(yintercept=4000),linetype="solid",size = 0.5)
a

a   +    annotate("text",label="0°C MAAT isoterma",x=0.8,y=4050,size=4)

Here the plot that I finally got! https://dl.dropbox.com/u/11320858/plot3.png

Editing legend (text) labels in ggplot

The tutorial @Henrik mentioned is an excellent resource for learning how to create plots with the ggplot2 package.

An example with your data:

# transforming the data from wide to long
library(reshape2)
dfm <- melt(df, id = "TY")

# creating a scatterplot
ggplot(data = dfm, aes(x = TY, y = value, color = variable)) + 
  geom_point(size=5) +
  labs(title = "Temperatures\n", x = "TY [°C]", y = "Txxx", color = "Legend Title\n") +
  scale_color_manual(labels = c("T999", "T888"), values = c("blue", "red")) +
  theme_bw() +
  theme(axis.text.x = element_text(size = 14), axis.title.x = element_text(size = 16),
        axis.text.y = element_text(size = 14), axis.title.y = element_text(size = 16),
        plot.title = element_text(size = 20, face = "bold", color = "darkgreen"))

this results in:

As mentioned by @user2739472 in the comments: If you only want to change the legend text labels and not the colours from ggplot's default palette, you can use scale_color_hue(labels = c("T999", "T888")) instead of scale_color_manual().

Change the symbol in a legend key in ggplot2

Adapting code for this answer:
The idea is to inhibit the geom_text legend, but to allow a legend for geom_point, but make the point size zero so the points are not visible in the plot, then set size and shape of the points in the legend in the guides statement

x <- rnorm(9); y <- rnorm(9); s <- rep(c("F","G","K"), each = 3)
df <- data.frame(x, y, s)
#
require(ggplot2)
#
ggplot(df, aes(x = x, y = y, colour = s, label = s)) +
   geom_point(size = 0, stroke = 0) +  # OR  geom_point(shape = "") +
   geom_text(show.legend = FALSE) +
   guides(colour = guide_legend(override.aes = list(size = 5, shape = c(utf8ToInt("F"), utf8ToInt("K"), utf8ToInt("G"))))) +
   scale_colour_discrete(name = "My name", breaks = c("F","K","G"), labels = c("Fbig","Kbig","Gbig")) 

Changing Legend Items ggplot

You can use scale_colour_gradient to set breaks, then change the labels.

library(tidyverse)

ggplot() +
  geom_line(data=mtcars,
              aes(x=cyl, y = mpg,
                  color=mpg)) +
  scale_colour_gradient(breaks = c(15, 20, 25, 30, 40),
                        labels = c("1+", "2+", "3+", "4+", "5+"))

Output

Format of key label text in legend in ggplot

Try the following:

scale_fill_distiller(name=expression(Confirmed~(log[10])), 
palette = "Spectral", trans = "log10", 
breaks = breaks_vec, 
labels = parse(text=c("1","10","100","1000","10^4","10^5"))) +
guides(fill=guide_legend(title=expression(Confirmed~(log[10]))))

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How can I change the title of a ggplot2 legend?

Add

+ labs(colour = "legend title") 

to your ggplot call.
Great resource site is also google group for ggplot2.

edit: this assumes that colour is the aesthetic in the legend, e.g. qplot(x,y,colour=z). If another aesthetic is being shown in the legend, use that as the argument instead, e.g. + labs(fill = "legend title") for a raster/image plot.

More generally, if you specify an explicit scale such as scale_colour_continuous, you can set the scale_name argument (warning: the details of the arguments to scales may have changed in recent releases of ggplot2; this description is of version 0.9.2.1).

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