get legend for two different data sets in ggplot-CodePudding

I am trying to create a legend from two different data sets. An example as below

ggplot(data = mtcars,aes(x = mpg, y = wt)) 
  geom_point(aes(colour = drat)) 
  geom_line(aes(colour = drat)) 
  geom_point(data = iris, aes(x = Sepal.Width, y = Petal.Length)) 
  geom_line(data = iris, aes(x = Sepal.Width, y = Petal.Length),linetype = "dashed") 
  scale_color_gradientn(colours=c('red','yellow','green'))

In the first data (mtcars) the color is according to a certain column value (drat). But in the second data (iris) it is just x and y points. How can I get line as the two lines as legend in addition to the color legend which is already present.

CodePudding user response：

Easiest way is to pass names to linetype within the aes() calls. The names become the legend labels. You can then use scale_linetype_manual to set linetypes there:

library(ggplot2)

ggplot(data = mtcars,aes(x = mpg, y = wt)) 
  geom_point(aes(colour = drat)) 
  geom_line(aes(colour = drat, linetype = "Cars")) 
  geom_point(data = iris, aes(x = Sepal.Width, y = Petal.Length)) 
  geom_line(data = iris, aes(x = Sepal.Width, y = Petal.Length,
                             linetype = "Iris")) 
  scale_color_gradientn(colours=c('red','yellow','green'))  
  scale_linetype_manual(values = c(
    "Cars" = "solid",
    "Iris" = "dotted"
  ))