Calculate an Expected Hits Matrix

Calculate the probability of a hit, walk, or out based on the ball–strike count.

The ball–strike count is one of the most important ways pitchers and hitters determine their strategy. Most batters will be ready to swing on an 0,2 (no balls, two strikes) count, but many batters won’t swing on a 3,0 count (three balls, no strikes). Of course, if the pitcher has generally good control, he might be able to throw the ball into the strike zone at this point, so it might be a good idea for the batter to swing. But then again, if the batter is planning to swing and the pitcher knows the batter is expecting a ball in the strike zone, the pitcher might decide to throw something unhittable and outside the strike zone…you get the idea. The count is at the core of baseball strategy. It drives the mental battle between the hitter and the pitcher.

This hack examines what is likely to happen on different counts. Clearly, a walk is more likely if the pitcher has thrown more balls, and a strikeout is more likely if the pitcher has thrown more strikes. But are extra base hits more likely in some situations? This hack shows you how to count the number of situations in which each of these things happened.

The Code

The key to understanding this code is to understand the possible set of counts and how a batter can move between them. Figure 6-4 illustrates how this works (the first number is the number of balls and the second is the number of strikes).

Figure 6-4. How the ...

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