How to put values on a boxplot for median, 1st quartile and last quartile?

Question

How to put values on boxplot and control its width?

X<-c(1,2,,3,4,4,5,5,6,6,6,6,6,7)

I need to write values for min, max, 1st quartile, median and last quartile. How can I put it there?

Answer 1

You can use horizontal = TRUE get a horizontal boxplot and axes = FALSE to remove the axes. staplewex = 1 sets the staple width the same as the box width

Then you can use fivenum to return the statistics used to create the boxplot and use these as text labels, fiddling with the y value until you have what you want

boxplot(X, horizontal = TRUE, axes = FALSE, staplewex = 1)
text(x=fivenum(X), labels =fivenum(X), y=1.25)

Note that i've inserted a 3 for the value missing in your example data X

Answer 2

The answer provided by mnel is perfect, assuming —as in the example— that there are not outliers. In that case, the lower and upper whiskers are then equal to the minimum and maximum. But, if there are outliers and we don't specify range = 0 in the boxplot function, we don't get the right values for the labels. Instead, we could use:

text(x=boxplot.stats(X)$stats, labels = boxplot.stats(X)$stats, y = 1.25)

Let's see an example:

Horizontally

X <- c(1,2,3,3,4,4,5,5,6,6,6,6,10,15)
boxplot(X, horizontal = TRUE, axes = FALSE, staplewex = 1)

1. Incorrect valuestext(x = fivenum(X), labels = fivenum(X), y = 1.25)

2. Correct values: text(x = boxplot.stats(X)$stats, labels = boxplot.stats(X)$stats, y = 1.25)

Vertically

Switching the arguments for x and y inside text.

boxplot(X, axes = FALSE, staplewex = 1)
text(y = boxplot.stats(X)$stats, labels = boxplot.stats(X)$stats, x = 1.25)