Remove a few text marks from tick marks in ggplot bar plot

Question

I am doing some research on non-defaulters and defaulters with regards to banking. In that context I am plotting their distributions relative to some score in a bar plot. The higher the score, the better the credit rating.

Since the number of defaults is very limited compared to the number of non-defaults plotting the defaults and non-defaults on the same bar plot is not very giving as you hardly can see the defaults. I then make a second bar plot based on the defaulters' scores only, but on the same interval scale as the full bar plot of both the scores of the defaulters and non-defaulters. I then add vertical lines to the first bar plot indicating where the highest and the lowest defaulter score is located. That is to get a view of where the distribution of the defaulters fit into that of the overall distribution of both defaulters and non-defaulters.

The x-axis easily gets very "crowded". I would like to remove some of the text for the ticks, but not all the tick marks.

Below is the code I am using replaced with (seeded) random data instead.

The first bar plot is what I would like to have with regards to text on the tick marks, but I am missing all the ticks I have in the second bar plot. In the second bar plot the "crowded"-ness is shown!

library(ggplot2)
library(ggExtra)

#NDS represents non-defaults and DS defaults on the same scale
#although here being just some random normals for the sake of simplicity.
set.seed(10)
NDS<-rnorm(10000,sd=1)-2
DS<-rnorm(100,sd=2)-5

#Cutoffs are constructed such that intervals of size 0.3 contain all values 
#of NDS & DS
minCutoff<--9.3
maxCutoff<-2.1

#Generate the actual interval "bins"
NDS_CUT<-cut(NDS,breaks=seq(minCutoff, maxCutoff, by = 0.3))
DS_CUT<-cut(DS,breaks=seq(minCutoff, maxCutoff, by = 0.3))

#Manually generate where to put the vertical lines for min(DS) and max(DS)
minDS_bar<-levels(cut(NDS,breaks=seq(minCutoff, maxCutoff, by = 0.3)))[1]
maxDS_bar<-levels(cut(NDS,breaks=seq(minCutoff, maxCutoff, by = 0.3)))[32]

#Generate data frame - seems stupid, but makes sense
#when the "real" data is used :-)
NDSdataframe<-cbind(as.data.frame(NDS_CUT),rep(factor("State-1"),length(NDS_CUT)))
colnames(NDSdataframe)<-c("Score","Action")
DSdataframe<-cbind(as.data.frame(DS_CUT),rep(factor("State-2"),length(DS_CUT)))
colnames(DSdataframe)<-c("Score","Action")
fulldataframe<-rbind(NDSdataframe,DSdataframe)
attach(fulldataframe)

#Plot the full distribution of NDS & DS with geom_vlines

#Get the tick texts I want to show
myLevels<-levels(cut(NDS,breaks=seq(roundDownNDS, roundUpNDS, by = 0.3)))
lengthMyLevels<-length(myLevels)
myBreaks<-seq(1,lengthMyLevels,3)
chosenbreaks<-myLevels[myBreaks[1]]
for(i in 2:length(myBreaks))
 {
 chosenbreaks<-rbind(chosenbreaks,myLevels[myBreaks[i]])
 }


#Generate the plot of both NDS & DS
fullplot<-ggplot(fulldataframe, aes(Score, fill=factor(Action,levels=c("State-    2","State-1")))) + geom_bar(position="stack") + opts(axis.text.x = theme_text(angle = 45,size=8))  + opts(legend.position = "none")    + xlab("Scoreinterval") + ylab("Antal pr. interval") + geom_vline(aes(xintercept = minDS_bar, colour="red")) + geom_vline(aes(xintercept = maxDS_bar, colour="red")) + scale_x_discrete("test",breaks=chosenbreaks)

#Generate second dataframe for the plot of DS only
DSdataframe2<-cbind(na.omit(as.data.frame(DS_CUT)),rep(factor("Fallit"),length    (na.omit(as.data.frame(DS_CUT)))))
colnames(DSdataframe2)<-c("theScore","theAction")

#Calculate max value for the DS
myMax<-max(table(DSdataframe2))+1

attach(DSdataframe2)

#Generate plot for the DS only
subplot<-ggplot(fulldataframe, aes(theScore, fill=factor(theAction))) + geom_bar   (position="stack") + opts(axis.text.x = theme_text(angle = 45))  + opts(legend.position = "none") + ylim(0, myMax) + xlab("Scoreinterval") + ylab("Antal pr. interval")

#Using the ggExtra package the to plots are aligned
align.plots(fullplot, subplot)

detach(DSdataframe2)
detach(fulldataframe)

Any help is very much appreciated!

Thanks,

Christian

Answer 1

If I understand correctly, you can simply specify empty text labels for every other label,

library(ggplot2)

interleave <- function(x,y){
  lx <- length(x)
  ly <- length(y)
  n <- max(lx,ly)
  as.vector(rbind(rep(x, length.out=n), rep(y, length.out=n)))
}

d <- data.frame(x=1:10, y=rnorm(10))

my_breaks <- seq(1,10,by=1)
my_labs <- interleave(seq(1,10,by=2), "")

qplot(x,y,data=d)+
  scale_x_continuous(breaks=my_breaks, labels=my_labs)