### Introduction

If you have been watching the 2017 MLB playoff games, it should be obvious is that much of the game is the contest between the pitcher and the batter, and a relatively small portion of the game is devoted to the action on the field such as balls put in play, defense, and running bases. From the batter’s perspective, there are two primary issues: (1) First should the batter swing or take the pitch? (2) If the batter does swing, then he wants to make contact. This motivates the consideration of two rates:

**Swing Rate** = the percentage of pitches that are swung at

**Miss Rate** = the percentage of swings that are missed completely (the so-called swinging strikes)

These two rates have a lot to do with strikeouts and walks. Players who are reluctant to swing tend to walk more often. Also, players with high swing rates and high miss rates tend to have a high rate of strikeouts.

### The 2017 World Series Teams

How do the players on the Dodgers and the Astros compare with respect to swing and miss rates? Here is a scatterplot of the swing and miss rates (percentages) for the Astros and Dodgers regulars.

Several observations from this scatterplot:

- The Astros (red) tend to have similar swing rates and there is more variability in the Dodger (blue) swing rates. Several Dodgers such as Utley and Barnes are reluctant to swing and other Dodgers such as Bellinger and Seager like to swing.
- With respect to miss rates, there is also more variation among the Dodgers regulars. Utley and Barnes are not likely to miss when they swing and Bellinger has a high miss rate. It is interesting that the five highest miss rates all are Dodgers.
- Jose Altuve has a high swing rate, but he has a low miss rate which partially explains his hitting success.

### Looking at Swing Locations

Okay we know batters vary with respect to swing rates, but where do they like to swing? The Statcast data contains the (x, y) coordinates for each pitch, and using a generalized additive model, one can estimate the probability of a swing at any pitch location. For each batter, I fit this model and the blue contour lines represent a 50% probability of a swing — points inside the contour have a probability of swing that exceeds 50%. Here are the swing contours for the Dodgers regulars. As one might expect, Barnes and Utley are likely to swing only in a small region inside the zone — in contrast, Bellinger, Seager, Pederson, and Puig are likely to swing in a large region.

Here is a similar graph for the Astros regulars. Note that Beltran and Gattis like to swing at pitches high in the strike zone (didn’t Evan Gattis hit a home run in the ALCS on a high pitch?). Also George Springer has a large swing zone. Jose Altuve appears to like to swing at balls near the center of the zone.

### Other Comments

- In modern baseball, I would think that the teams are well-aware of batters’ swinging tendencies. The Dodgers and Astros are among the top teams with respect to analytics and I would think that the coaching staff would be provided graphs such as these to inform the pitchers.
- The data was downloaded as csv files from the Statcast Search page of Baseball Savant. All of the R code for the graphs and the generalized additive modeling is available from my gist site.