Add whiskers (horizontal lines) to multiple boxplots

Question

I need to add whisker (or horizontal lines) to my multiple box-plots.

You can find my dataset here: link to data is broken...

In other words, I am plotting three variables (Mat, Ita, and Log) divided by Gender (F and M), in order to compare their box plots. I need to add an horizontal line at the end of both vertical lines in each box plot.

I am using ggplot2 package and the code I am using so far is (this code allows me to create the box plots as I need them, I only need to add the horizontal lines):

ggplot(newdata,aes(x=variable,y=value)) + 
  geom_boxplot(aes(fill=Gender)) + 
  xlab("Subject") + 
  ylab("Quiz score") + 
  ggtitle("Boxplots for quiz score and gender") + 
  scale_fill_manual(values=c("pink","lightblue"),labels=c("Female","Male")) + 
  theme(plot.title = element_text(face="bold"))

mpalanco mpalanco · Accepted Answer · 2015-07-07T08:07:54

You could use stat_boxplot(geom ='errorbar')

I provide an example:

bp <- ggplot(iris, aes(factor(Species), Sepal.Width, fill = Species))
bp + geom_boxplot() + stat_boxplot(geom ='errorbar')

Result:

enter image description here

Add whiskers (horizontal lines) to multiple boxplots

1 Answers