Question

I want to combine two ggplots, from two different data.frames, into one plot. Below you will find the code. I want to combine plot 1&2 or plots 3&4.

df1 <- data.frame(p=c(10,8,7,3,2,6,7,8),
             v=c(100,300,150,400,450,250,150,400))
df2 <- data.frame(p=c(10,8,6,4), v=c(150,250,350,400))

plot1 <- qplot(df1$v, df1$p)
plot2 <- qplot(df2$v, df2$p, geom="step")

plot3 <- ggplot(df1, aes(v, p)) + geom_point()
plot4 <- ggplot(df2, aes(v, p)) + geom_step()

This must be very easy to do, but somehow I can’t get it to work. Thanks for your time.

Answer 1

As Baptiste said, you need to specify the data argument at the geom level. Either

#df1 is the default dataset for all geoms
(plot1 <- ggplot(df1, aes(v, p)) + 
    geom_point() +
    geom_step(data = df2)
)

or

#No default; data explicitly specified for each geom
(plot2 <- ggplot(NULL, aes(v, p)) + 
      geom_point(data = df1) +
      geom_step(data = df2)
)