Question

I am struggling to display two barcharts side by side with the same scale

My code looks like this

library(ggplot2)
library(gridExtra)
#dataframe definition
rm(list=ls(all=TRUE))
mydata <- data.frame(a=1:10,b=c('yes','no'),c=seq(2,20,2))

plot1<- ggplot(mydata, aes(x=factor(mydata$b), y=100*a), order=f, fill=grey) + 
  stat_summary(fun.y="mean", geo    m="bar", colour="black")+xlab("Factor b") + 
  ylab("Value of a")    

plot2<- ggplot(mydata, aes(x=factor(mydata$b), y=c), order=f) + 
  stat_summary(fun.y="mean", geom="bar", colour="black")+xlab("Factor b") + 
  ylab("Value of b")    

grid.arrange(plot1, plot2, ncol=2)

That produces the following image.

I want to position them in a way the vertical axis has the same scale for both of the barcharts.
I couldn’t find any documentation on the gridExtra manual.

Answer 1

What about something like this?

library(ggplot2)
library(reshape2)

mydata <- data.frame(a=1:10,b=c('yes','no'),c=seq(2,20,2))
df <- melt(mydata, id.vars="b")
df[which(df$variable=="a"),]$value <- df[which(df$variable=="a"),]$value * 100
ggplot(df, aes(factor(b), value))  + 
  stat_summary(fun.y="mean", geom="bar", colour="black") + facet_grid(.~variable)


# If you need free scales, then:

ggplot(df, aes(factor(b), value))  + 
  stat_summary(fun.y="mean", geom="bar", colour="black") + 
  facet_wrap( ~variable, scales = "free_y")