Phattrawan Tongkumchum

pp. 859 - 866

Abstract

In this paper we propose a two-dimensional box plot, a simple bivariate extension of the box plot and
the scatter plot. This plot comprises a pair of trapeziums oriented in the direction of a fitted straight line, with
symbols denoting extreme values. The choice for the fitted straight resistant line showing the relationship
between the two variables is Tukey’s resistance line. The main components of the plot are an inner box
containing 50% of the projection points of the observations on the fitted line, a median point inside the inner
box, and an outer box that separates outliers. The two-dimensional boxplot visualises the location, spread,
correlation and skewness of the data.

Keywords

• two-dimensional box plot
• bivariate graphical display
• bivariate box plot
• Tukey’s line