How to set the distance between discrete values in ggplot2? - r

Question

I am attempting to use grid.arrange to plot several graphs in one column, as the x axis is the same for all graphs. However the different graphs have different number of discrete values, resulting in Samples in the top graph more distanced than the graph below. Is there a way to set the distance between discrete values on an axis so the distance between Sample1 and Sample2 lines is the same for both graphs? Thanks!
Here is an example:
library(reshape2)
library(tidyverse)
library(gridExtra)
#Data frame 1
a <- c(1,2,3,4,5)
b <- c(10,20,30,40,50)
Species <- factor(c("Species1","Species2","Species3","Species4","Species5"))
bubba <- data.frame(Sample1=a,Sample2=b,Species=Species)
bubba$Species=factor(bubba$Species, levels=bubba$Species)
xm=melt(bubba,id.vars = "Species", variable.name="Samples", value.name = "Size")
#Data frame 2
c <- c(1,2,3,4,5)
d <- c(10,20,30,40,50)
e <- c(1,2,3,4,5)
f <- c(10,20,30,40,50)
bubban <- data.frame(Sample1=c,Sample2=d,Sample3=e,Sample4=f,Species=Species)
xn=melt(bubban,id.vars = "Species", variable.name="Samples", value.name = "Size")
#Not related, but part of my original script i am using
shrink_10s_trans = trans_new("shrink_10s",
transform = function(y){
yt = ifelse(y >= 10, y*0.1, y)
return(yt)
},
inverse = function(yt){
return(yt) # Not 1-to-1 function, picking one possibility
}
)
#Make plot 1
p1=ggplot(xm,aes(x= Species,y= fct_rev(Samples), fill = Size < 10))+
geom_point(aes(size=Size), shape = 21)+
scale_size_area(trans = shrink_10s_trans, max_size = 10,
breaks = c(1,3,5,10,20,30,40,50),
labels = c(1,3,5,10,20,30,40,50)) +
scale_fill_manual(values = c(rgb(136,93,100, maxColorValue = 255),
rgb(236,160,172, maxColorValue = 255))) +
theme_bw()+theme(axis.text.x = element_text(angle = -45, hjust = 1))+scale_x_discrete(position = "top")
#Make plot 2
p2=ggplot(xn,aes(x= Species,y= fct_rev(Samples), fill = Size < 10))+
geom_point(aes(size=Size), shape = 21)+
scale_size_area(trans = shrink_10s_trans, max_size = 10,
breaks = c(1,3,5,10,20,30,40,50),
labels = c(1,3,5,10,20,30,40,50)) +
scale_fill_manual(values = c(rgb(136,93,100, maxColorValue = 255),
rgb(236,160,172, maxColorValue = 255))) +
theme_bw()+theme(axis.text.x = element_blank())
#arrange the plots
grid.arrange(p1,p2,nrow=2)

Answer 1

Instead of using grid.extra use ggpubr::ggarrange function. It lets you specify heights of each plot and set shared legend.
# Using plots generated with OPs code
ggpubr::ggarrange(p1, p2, nrow = 2, heights = c(1.3, 2),
common.legend = TRUE, legend = "right")
With argument heights you can set relative heights of each provided plot.