Second Y-Axis in ggplot (R) [duplicate] - r

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ggplot with 2 y axes on each side and different scales
(18 answers)
Closed 4 years ago.
I am trying to make a plot with ggplot in a Shiny app in R and I need to set a second Y-axis in it. This plot has two types of graphics: lines and bars. I would like to represent the bars (depth of precipitation) on the left, and the lines (flows) on the right.
My current code is:
output$plotRout <- renderPlot({
ggplot(totalRR(),aes(x=time)) +
geom_bar(aes(y=mm), stat = "identity",fill = "dodgerblue",color = "black") +
geom_bar(aes(y=NetRain), stat = "identity",fill = "Cyan",color = "black") +
geom_line(aes(y=DirRun, colour = "Direct Runoff"), stat = "identity",color = "Red") +
geom_line(aes(y=BF, colour = "Baseflow"), stat = "identity",color = "Darkorange", linetype = "longdash") +
scale_y_continuous("Rainfall (mm)", sec.axis = sec_axis(~.*10, name = "Flow (m3/s)")) +
xlab("Time (h)")
})
The result is:
This plot has on the left the values of the flows, the values that should be on the right, whereas the values of rainfall (the bars) are not displayed on the plot.
How could I make this plot putting the values of the bars (rainfall) on the left and the second y-axis on the right showing the values of the lines (flows)?
Many thanks in advance.
Victor

Answer 1

One solution would be to make the Flow axis your primary y axis. This involves 1) scaling the data using *10 and then 2) transforming the secondary axis using /10 to get back the correct numbers for the Rainfall axis:
ggplot(totalRR(),aes(x=time)) +
geom_bar(aes(y=10*mm), stat = "identity",fill = "dodgerblue",color = "black") +
geom_bar(aes(y=10*NetRain), stat = "identity",fill = "Cyan",color = "black") +
geom_line(aes(y=10*DirRun, colour = "Direct Runoff"), stat = "identity",color = "Red") +
geom_line(aes(y=10*BF, colour = "Baseflow"), stat = "identity",color = "Darkorange", linetype = "longdash") +
scale_y_continuous("Flow (m3/s)", sec.axis = sec_axis(~./10, name = "Rainfall (mm)")) +
xlab("Time (h)")