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Friday, June 19, 2009
hSOB (Horizontal Speed off the bat)
Someone asked Dave Allen:
Is that a more accurate measure than just taking the average overall speed, or just a preference?
And he responded:
I guess it is preference and depends on what you are trying to say. In this case I wanted some proxy for how ‘hard’ the balls are hit and I think that horizontal speed is a better measure of that than overall speed.
Additionally horizontal speed does seem to be a better predictor of success of a ball in play. To see that you can plot the run value of a ball in play against the overall speed (like you did at your blog) and horizontal speed and then fit a line to both. In both cases you get a tiny p-value so both overall speed and horizontal speed predict success, but the r-squared for the horizontal speed is a little bit higher than for the overall speed. I get about r^2 = 0.136 versus r^2 = 0.103. So the horizontal speed explains another 3% more of the variation in run value outcome than the overall speed.
Let’s say that our objective is to figure out how hard a ball is hit. Not just to figure out how hard in its most pure form, but how hard as in a ball that travels far, fast, and is tough to field. The horizontal speed off the bat (hSOB) seems to give us what we want. That is, we are measuring the speed of the ball off the bat by only looking at the horizontal component (vertical launch angle of 0 degrees). After all, we want the ball to move forward. But, we also want some, not alot, of loft. And, as has been pointed out by a few PITCHf/x-ers now, the ideal vertical launch angle is around 11 degrees.
Therefore, shouldn’t we measure the speed off the bat at 11 degrees, rather than 0 degrees? Furthermore, some power hitters, say Ryan Howard, have the optimum launch angle at say 25 degrees.
In other words, how hard you hit the ball is really another way of saying “how much of that ball did he get” (with the understanding that you don’t want to hit the ball flush on, but a tiny bit below the center point). And, that amount is entirely determined based on the plane of his swing.
So, while hSOB gives us part of what we want, if the question is “how hard did he hit the ball”, shouldn’t we solve that based on the plane of the hitter’s swing (which we can possibly infer based on the average of all his trajectories, or possibly based on the average of all his hits)?
Am I thinking about this wrong?
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