# Labelled Points in plot of lm.fit [duplicate]

The image shown below is the output for plot(lm.fit) on the Boston dataset, where lm.fit=lm(medv~lstat) . Why are some of the points labelled in the plot ?

• This is purely a matter of reading the documentation. The help page for plot.lm, which is the function that produced these plots, states "id.n: number of points to be labelled in each plot, starting with the most extreme" is the argument controlling how many points will be labeled. By default this value is 3 (as the source code attests). The source code also shows that "extreme" means "largest absolute residuals."
– whuber
May 19, 2017 at 13:45