I have a data set of events with year, gender and some other data. I'd like to draw a dotplot that shows one dot per event

I reproduced the problem with this test data set. Here's the setup:

library(ggplot2)

gender<-c("f","f","f","f","m","m","m","m","m","m","m")
year<-c(2002, 2005, 2009, 2011, 2015, 2002, 2021, 2009, 2011, 2006,2015)

testdata<-as.data.frame(cbind(gender, year))

And here's the code I'm having a problem with:

table(testdata$year,testdata$gender)
ggplot(testdata, aes(x=year, fill=gender)) geom_dotplot()

Somehow, even though the table shows all eleven events, just eight are appearing on the dotplot. Whenever a year should have two colors/fills, as in 2009 & 2011, it displays only one. I can tell it's not a stacking problem because 2015, with 2 instances of one color, appears just fine. Why don't I see two dots of different colors in 2009 and 2011?

CodePudding user response：

It actually is a stacking problem. The following solves:

ggplot(testdata, aes(x=year, fill = gender))  
  geom_dotplot(position = "dodge")

In 2015 you see two dots of the same color, since the default option for geom_dotplot() is to stack in the upper direction dots from the same group. However, picking 2002 as example, this does not apply since automatically. position = "dodge solves.