Baseball Hacks

Compare Teams Using Chernoff Faces

Use your innate ability to recognize facial features to compare teams.

People are naturally very good at recognizing visual patterns, particularly similarities and differences in human faces. In 1973, statistician Herman Chernoff developed a novel technique for comparing data points: plot data points as human faces, where each facial characteristic (mouth size, mouth expression, face shape, eye shape, etc.) represents a different variable in the data. This hack shows you how to apply this idea to baseball teams (or to anything else that you want to compare).

I found two sources of free code for plotting Chernoff faces. The first is from Dr. Hans Peter Wolf. You can find the code on his home page at http://www.wiwi.uni-bielefeld.de/~wolf. The second source is from Shigenobu AOKI, available at http://aoki2.si.gunma-u.ac.jp/R/face.html. In this book, I use Dr. Wolf’s code. (It doesn’t implement the original algorithm exactly, but it’s a lot easier to use.) Just copy all the code from http://www.wiwi.uni-bielefeld.de/~wolf/software/R-wtools/faces/faces.R, paste it into your R window, and hit Return. Or, easier yet, you can just use R’s source() command to load the code in one step. (I show this in the next section.)

Dr. Wolf’s faces() code requires a matrix of values to run. The data in the first column controls the height of the face, the data in the second controls the width, and so on. (See his site for the complete details.) Here are mappings you ...