X-axis labels on top out of the plot area

Question

I'm plotting a correlation heatmap with x-axis on top by using switch_axis_position. The x-axis labels are somewhat long, so I want it to be rotated by using angle=90 and align them by using hjust=0. But this makes the labels too far from the x-axis and even gets them out of the plot area.

library(gtable)
library(cowplot)
library(grid)

heatmap<-ggplot(data=meltedh, aes(x=variable, y=X, fill=value))+
  geom_tile(color="White")+
  ylab("")+xlab("")+
  scale_fill_gradient2(low="blue3", high="red3", mid="white", 
                      midpoint=0,limit=c(-1,1), space="Lab", breaks=c(-0.5,0,0.5),
                      name="Correlation Coefficient")+
  theme(legend.position="bottom", 
        axis.text.x=element_text(angle=90, hjust=0))
heatmap
ggdraw(switch_axis_position(heatmap,axis='x'))

How can I make this pretty? Any help would be great. Thanks.

Answer 1

Lucky for you I rather enjoy making up data.

So this might be what you want. I did the following things:

• Played with hjust to get it close to looking okay
• Padded the names with spaces to make them all the same length
• Changed the font family to "mono", so the axis text would be aligned

library(gtable) library(cowplot) library(grid)

set.seed(1234)
cn <- c("Eastside","Pygrate","Tapeworm","Annerose","Bund",
        "Mountain","Appalacia","Summer","Treasure","Riveria",
        "Persia","Raggout","Bengal","Siam","Norman")

# Pad out the names with spaces to all be the same length
mxl <- max(nchar(cn))
fmt <- sprintf("%%-%ds",mxl)  # the minus adds spaces to the string end
cn  <- sprintf(fmt,cn)

rn <- rev(letters[1:16])

ddf <- expand.grid( x=rn, y=cn )
n <- nrow(ddf)
ddf$v <- runif(n,-1,-0.1)

nr <- n/length(cn)
ddf[ddf$y==cn[3],]$v <- runif(nr,0.1,0.8)
ddf[ddf$y==cn[8],]$v <- runif(nr,0.1,0.8)
ddf[ddf$y==cn[13],]$v <- runif(nr,0.1,0.8)
ddf[ddf$x %in% c("i","j","n","o"),]$v <- 0


meltedh <- data.frame(X=ddf$x,variable=ddf$y,value=ddf$v)

heatmap<-ggplot(data=meltedh, aes(x=variable, y=X, fill=value))+
  geom_tile(color="White")+
  ylab("")+xlab("")+
  scale_fill_gradient2(low="blue3", high="red3", mid="white",
                       midpoint=0,limit=c(-1,1), space="Lab", breaks=c(-0.5,0,0.5),
                       name="Correlation Coefficient")+
  theme(legend.position="bottom", 
        axis.text.x=element_text(angle=90, hjust=0.5,family="mono"))

heatmap
ggdraw(switch_axis_position(heatmap,axis='x'))

It yields this: