The method for calculating the ellipses has been modified from
car::ellipse
(Fox and Weisberg, 2011)
1 2 3 
mapping 
Set of aesthetic mappings created by 
data 
The data to be displayed in this layer. There are three options: If A A 
geom 
The geometric object to use display the data 
position 
Position adjustment, either as a string, or the result of a call to a position adjustment function. 
... 
other arguments passed on to 
type 
The type of ellipse.
The default 
level 
The confidence level at which to draw an ellipse (default is 0.95),
or, if 
segments 
The number of segments to be used in drawing the ellipse. 
na.rm 
If 
show.legend 
logical. Should this layer be included in the legends?

inherit.aes 
If 
John Fox and Sanford Weisberg (2011). An R Companion to Applied Regression, Second Edition. Thousand Oaks CA: Sage. URL: http://socserv.socsci.mcmaster.ca/jfox/Books/Companion
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21  ggplot(faithful, aes(waiting, eruptions)) +
geom_point() +
stat_ellipse()
ggplot(faithful, aes(waiting, eruptions, color = eruptions > 3)) +
geom_point() +
stat_ellipse()
ggplot(faithful, aes(waiting, eruptions, color = eruptions > 3)) +
geom_point() +
stat_ellipse(type = "norm", linetype = 2) +
stat_ellipse(type = "t")
ggplot(faithful, aes(waiting, eruptions, color = eruptions > 3)) +
geom_point() +
stat_ellipse(type = "norm", linetype = 2) +
stat_ellipse(type = "euclid", level = 3) +
coord_fixed()
ggplot(faithful, aes(waiting, eruptions, fill = eruptions > 3)) +
stat_ellipse(geom = "polygon")

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