How to add a legend for two geom layers in one ggplot2 plot?
In ggplot, legends are automatically created for mapped aesthetics. You can add such mappings as follows:
ggplot(data = df,
mapping = aes(x = x)) +
# specify fill for bar / color for line inside aes(); you can use
# whatever label you wish to appear in the legend
geom_col(aes(y = y.bar, fill = "bar.label")) +
geom_line(aes(y = y.line, color = "line.label")) +
xlab("Month of year") +
scale_y_continuous(name = "Daily classifications per Spotter") +
# the labels must match what you specified above
scale_fill_manual(name = "", values = c("bar.label" = "grey")) +
scale_color_manual(name = "", values = c("line.label" = "black")) +
theme_bw()
In the above example, I've also moved the data & common aesthetic mapping (x) to ggplot()
.
Sample dataset:
set.seed(7)
df <- data.frame(
x = 1:20,
y.bar = rpois(20, lambda = 5),
y.line = rpois(20, lambda = 10)
)