R : How to plot two different kind of plot with ggplot2?

Question

My data is like this :

id <- c('a','a','b','b')
var <- c('Var1','Var2','Var1','Var2')
value <- c(123,421,2132,633)
df <- cbind(id,var,value)

I would like to plot a scatter plot of Var1 and a bar chart of Var2, with a legend showing that the dot is Var1 and the Bar is Var2

I have tried these code :

g <- ggplot(data = df, aes(x=id, y=value, fill=var)
g + stat_identity(geom = c("point","bar"))

But both Var1 and Var2 are showed in scatter point in this way.

I also tried to create two seprate data for Var1 and Var2.

id = c('a','b')
Var1 = c(123,2132)
Var2 = c(421,633)
df1 = cbind.data.frame(id, Var1)
df2 = cbind.data.frame(id, Var2)

g <- ggplot()
g + geom_point(data = df1, aes(x=id, y=Var1),stat = "identity")) +
    geom_bar(data = df2, aes(x=id, y=Var2),stat = "identity"))

In this way, I can combine a scatter point with a bar chart, but there is no legend and I don't know how to make the legend telling readers that the dot is Var1 and the bar is Var2

Have you realy applied the example code that you are giving? I am asking because the both appraoches generate data of class matrix, which cannot be used directlyin ggplot. Also, the ggplot in the second approach does not work, because you close to many brackets. Lastly, have you checked other threads on SO, such as this one — Daniel
– Daniel, Commented Jul 20, 2016 at 16:23
indeed i don't think you can do it without splitting the data (outside or inside ggplot) — agenis - code en bois
– agenis - code en bois, Commented Jul 20, 2016 at 16:24

Community · Accepted Answer · 2017-05-23 11:58:57Z

1

First off, see this post. Thanks @Daniel!

You could try this:

id = c('a','b')
Var1 = c(123,2132)
Var2 = c(421,633)
df1 = cbind.data.frame(id, Var1)
df2 = cbind.data.frame(id, Var2)
library(ggplot2)
g <- ggplot()
g + geom_bar(data = df2, aes(x=id, y=Var2, fill = 'Var2'),stat = "identity")+
     geom_point(data = df1, aes(x=id, y=Var1, colour = 'Var1'),stat = "identity", size = 2) +
    scale_fill_manual(values = c('Var2' = 'blue'), name = 'Bars')+
    scale_colour_manual(values = c('Var1' = 'red'), name = 'Dots')

Basically, we use the aes within geom_point and geom_bar to define our color or fill. Then use scale_*_manual to control display. Also, we call geom_bar before geom_point so that the dots are plotted over the bar. Also, I use size = 2 in geom_point so that the point is a little more distinguishable.

edited May 23, 2017 at 11:58

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answered Jul 20, 2016 at 16:21

bouncyball

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1 Comment

Daniel Over a year ago

I would just add the link to this question, where different variants are explained for a line plot.

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