To illustrate different methods for plotting 3-dimensional data, I collected some shooting data from the 12 MAC women basketball teams. There are three measures of shooting accuracy:
FGA – field goal shooting percentage
FTA – free throw shooting percentage
3FGA – three-point field goal shooting percentage
I’m interested in exploring the relationships between these three measures.
1. First, I try a three-dimensional scatterplot. The plot3d function (package rgl) constructs the plot and allows you to spin it around to see better the structure. Here’s a video of the spinning scatterplot. (Click the below link. I’ve colored BGSU as red; the rest of the points are colored blue.)
From this viewpoint, BGSU looks pretty average from the viewpoint of shooting accuracy. They did pretty well in the league standings, but I don’t think their success was due to shooting percentage.
2. Another thing to try is a scatterplot of all possible pairs of variables.
BGSU still corresponds to the red point and the blue points are the three teams with the highest values of FGA. We see that these good FGA teams also do well in Free Throw Shooting Percentage. These three teams are above average in Three Point Shooting Percentage, but I notice the team with the highest 3-Point Percentage is not one of these three teams. Generally, there are not strong relationships between these three variables.
3. Another thing to try is a coplot — here you condition on one variable and look at the conditional scatterplots of the other two variables. Here I condition on FTA and look at scatterplots of FGA and 3FGA.
This is harder to read. Look at the lower-left scatterplot — this is a scatterplot of FGA and 3FGA for the teams with a poor FTA percentage. The bottom center plot is a scatterplot of FGA and 3FPA for the teams with a slightly better FTA, and so on.
Focus on the bottom left and top right scatterplots — these are the scatterplots for the poor and strong foul shooting teams. Generally, poor foul shooting teams also are poor in the other two shooting stats; likewise great foul shooting teams are good in other two measures.