在R中的组合条形图中放置次要y轴

Question

I am combining two bar graphs using R that have the same Y-axes so I want to drop the second one as in B:

I found a way to do so using ggplot2 but just wondering if its possible within the barplot feature.

Thanks in advance!

Answer 1

barplot does this right out of the box. To illustrate, let's create the data represented by the two plots:

a <- c(2,4,6,8,9)
b <- c(5.5,6.5,7.5,8.5,9)

Here is the color vector to parallel c(a,b) :

col <- unlist(mapply(rep, c("#fb0019", "#8767fc"), c(2,3, 1,4)))

In this environment, just one function call does it all:

barplot(cbind(a, b), beside=TRUE, space=c(0.2, 1.2), names.arg=c("", ""), col=col)

This method passes the two vectors of data as columns of a matrix ( via cbind(a, b) ), causing it to produce two groups of bars. The values of space give, respectively, the relative spacing between within-group bars and between the groups. Finally, names.arg suppresses the automatic group labels that would be posted and col=col determines the colors of the bars from left to right.

Answer 2

To make both graphs stand closer to each other, like in your example, you need to meddle with par() a bit and I'm not sure which arguments do you need to mess with.

If you just need to get rid of the axis you can use axes=F inside the barplot function. Just be sure to specify the y axis range so you know both graphs are using the same scale.

a=c(1,2,3)
b=c(2,3,4)

par(mfrow=c(1,2))

barplot(a,ylim=c(0,5))
barplot(b,ylim=c(0,5),,axes=F)