Line plot with bars in secondary axis with different scales in ggplot2

Question

I'm trying to plot a line graph (data points between 0 and 2.5, with interval of 0.5). I want to plot some bars in the same chart on the right-hand axis (between 0 and 60 with interval of 10). I am making some mistake in my code such that the bars get plotted in the left hand axis.

Here's some sample data and code:

Month <- c("J","F","M","A")
Line <- c(2.5,2,0.5,3.4)
Bar <- c(30,33,21,40)
df <- data.frame(Month,Line,Bar)

ggplot(df, aes(x=Month)) +
  geom_line(aes(y = Line,group = 1)) +
  geom_col(aes(y=Bar))+
  scale_y_continuous("Line",
                     sec.axis = sec_axis(trans= ~. /50, name = "Bar"))

Here's the output

Thanks in advance.

Duck · Accepted Answer · 2020-09-03 12:34:35Z

1

Try this approach with scaling factor. It is better if you work with a scaling factor between your variables and then you use it for the second y-axis. I have made slight changes to your code:

library(tidyverse)
#Data
Month <- c("J","F","M","A")
Line <- c(2.5,2,0.5,3.4)
Bar <- c(30,33,21,40)
df <- data.frame(Month,Line,Bar)
#Scale factor
sfactor <- max(df$Line)/max(df$Bar)
#Plot
ggplot(df, aes(x=Month)) +
  geom_line(aes(y = Line,group = 1)) +
  geom_col(aes(y=Bar*sfactor))+
  scale_y_continuous("Line",
                     sec.axis = sec_axis(trans= ~. /sfactor, name = "Bar"))

Output:

answered Sep 3, 2020 at 12:34

Duck

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2 Comments

wellokaythen Over a year ago

Perfect! One more request: how to label the bars? Adding > geom_text(aes(label=Bar)) doesn't seem to work. Thanks a lot

Duck Over a year ago

@wellokaythen I would suggest you to add the labels after each geom so like this: geom_col(aes(y=Bar*sfactor))+geom_text(aes(y=Bar*sfactor,label=Bar)) !

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