Monday, September 26, 2016
Statcast NoLab: What is the infield?
?So Jeff highlights the "infield" and "pop up" issue. This has long been an issue that's been hidden from those who never delve into the batted ball stats. What's a grounder? What's a liner? What's a popup?
Think about this: you hit a ball that the SS catches on the fly, and that's a liner. But, if he is standing 10 feet farther back, and one-hops it, that's a ground ball. Same exit speed, same launch angle, same spray angle, same spin rate, same spin axis, same bat channel. But where the SS is positioned and how he plays that ball determines whether it's a grounder or liner. Analytically speaking, this doesn't help me at all. It helps the VIEWER, because the viewer is outcome-driven. Does it help me as an analyst? Not at all.
How about infield flies and popups? What ARE those? Well, from a viewer standpoint, you can define it however it is that you need to get the message across. A 300 foot flyball that took 8 seconds to reach the LF who didn't move one foot? Sure, call that a "popped-out". A SS that is standing 150 feet from home plate who doesn't move, but is otherwise standing behind the infield dirt: do you want to call that an "infield" fly or not? I don't know. Whatever it is that helps the VIEWER.
But analytically? SS and 2B position themselves normally 130 to 160 feet from home plate. SS and 2B are infielders. So, an air ball that is in the air for 5 seconds that travelled 150 feet would need to be an infield air ball of some sort, whether you call that an infield fly or infield popup or whathaveyou.
Alot of what we do is ORGANIZING data. That is what Barrels was all about: how do we organize well-struck balls? Everything we do is to try to organize data into some set of manageable categories. Without that, we are left with 100,000 unique batted balls (which they are, like snowflakes). But, that doesn't help anyone.
So, first figure out if your audience is the VIEWER or the ANALYST. Then categorize appropriately. And if you have two masters, then you need two definitions. That's just the way it works. As best you can, try to get them to overlap as much as possible. But sometimes, you can't. And that's when you need to create dual sets non-dueling metrics.
For whatever it's worth, I mark any infielder that is playing more than 220 feet from home plate as "outfield". And any outfielder that is playing less than 200 feet from home plate as "infield". Again, it doesn't matter what exactly is an infield and outfield. They are just useful terms. I just know that analytically, drawing the lines like that allows me to organize the data in the way that I need it.
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