Adding legend to a multi-histogram ggplot

user1701545 Published at Dev

user1701545

I'm trying to add a legend to a ggplot of two histograms, that may overlap and therefore would like to have them slightly transparent:

library(ggplot2)
set.seed(1)
plot.df <- data.frame(x=c(rnorm(1000,30,1),rnorm(10000,40,5)),
                      group=c(rep("a",1000),rep("b",10000)))

using:

ggplot(plot.df,aes(x=x,fill=factor(group)))+ 
  geom_histogram(data=subset(plot.df,group=='a'),fill="red",alpha=0.5)+
  geom_histogram(data=subset(plot.df,group=='b'),fill="darkgray",alpha=0.5)+
  scale_colour_manual(name="group",values=c("red","darkgray"),labels=c("a","b"))+scale_fill_manual(name="group",values=c("red","darkgray"),labels=c("a","b"))

but all I get is:

What's missing?

Psidom

Instead of plotting the two hisgrams separately, you can specify the fill parameter in the mapping as the group variable, in which case the legend will be automatically generated.

ggplot(plot.df, aes(x=x, fill = group)) + 
  geom_histogram(alpha = 0.5) + 
  scale_fill_manual(name="group",values=c("red","darkgray"),labels=c("a","b"))

Borrowed from here, the trick lies in setting up the fill parameter in the mapping(i.e aes here) of each of the histogram plot and then you can use scale_fill_manual normally:

ggplot(plot.df,aes(x=x))+ 
    geom_histogram(data=subset(plot.df,group=='a'),aes(fill=group),alpha=0.5)+
    geom_histogram(data=subset(plot.df,group=='b'),aes(fill=group),alpha=0.5)+
    scale_fill_manual(name="group", values=c("red","darkgray"),labels=c("a","b"))

Collected from the Internet

Please contact [email protected] to delete if infringement.

edited at2021-03-4

Comments

0 comments

From Dev

Related Related

Article

Adding legend to a multi-histogram ggplot

Adding legend to a multi-histogram ggplot

Adding manual legend in ggplot

adding values to ggplot legend

Adding external legend to ggplot

Adding a legend to an histogram plot that has several stat_bin layers using ggplot2

Add legend to ggplot histogram with overlayed density plots

Creating multi column legend in ggplot

Adding a legend to the ggplot map with shape

Adding legend in ggplot2

Adding a bar chart to a ggplot2 legend

Adding legend to a single line chart using ggplot

Adding a legend to a ggplot - invalid color name

Adding a manual legend in ggplot2?

Adding a point to the ggplot messes up the legend

R - Adding legend to ggplot graph for regression lines

Adding a bar chart to a ggplot2 legend

adding value stored in a variable as a legend in ggplot

Adding a density line to a histogram with count data in ggplot2

Adding a density line to a histogram with multiple variables in ggplot2

Left align multi-row ggplot2 legend

Adding greek symbols to legend ggplot (more than one)

Adding legend title and main title in ggplot2

Adding legend to ggplot2 with multiple lines on plot

Adding a custom legend to a blank ggplot2 line graph

R adding legend and directlabels to ggplot2 contour plot

adding custom ggplot legend to dashed lines and confidence bands

Adding legend to ggplot when lines were added manually

Adding a legend to ggplot when using stat_function

Adding a custom legend to a blank ggplot2 line graph

R adding legend and directlabels to ggplot2 contour plot