ABSTRACT
This chapter presents a handful of defensive metrics with the goal of using these measures to evaluate the fielding of shortstops during the 2009 season. The majority of defensive metrics are derived through basically the same process. Each measure compares the number of successful plays of a fielder with the expected number an average fielder would make with the same opportunities and translates the extra plays made into runs saved to the team. Data for several other defensive metrics can be downloaded from the Fan-Graphs website. Some of the players have played very little at the shortstop position in 2009 and thus may not have been rated by one or more of the selected defensive metrics. The function cor computes pairwise correlations between the various defensive metrics contained in the data frame defense. Data in the jetrol data frame require a little reshaping in order to be easily processed through one of the powerful graphics packages.
