ggplot combining two plots from different data.frames

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) ) 

Answer 2

The only working solution for me, was to define the data object in the geom_line instead of the base object, ggplot.

Like this:

ggplot() +  geom_line(data=Data1, aes(x=A, y=B), color='green') +  geom_line(data=Data2, aes(x=C, y=D), color='red') 

instead of

ggplot(data=Data1, aes(x=A, y=B), color='green') +  geom_line() +  geom_line(data=Data2, aes(x=C, y=D), color='red') 

More info here