Park adjusting DER

[AstrosFan]

Is there a simple way to do it?

[SABR Matt]

Not a simple way to park-adjust DER...but IMHO there's a simple way to park adjust runs not produced by the longball.

RA = LWHR * HR + All the rest
if you take the HR runs out, you can park adjust the non-HR runs using a non-HR park factor.

One of the data products the F/S Matrix produces is an in-play park factor that is mathematically pure.

PkI = PkR - PkHR*LWHR (PkI = Park in play factor)

I can do that because the park factors are all in terms of runs per game per team above average so they can be directly added.

Take an F/S Park-I, multiply it by games played and there's the number of runs you must subtract from the non-HR runs to get a park adjusted in-play run score.

[AstrosFan]

---Wincing

[SABR Matt]

Oh come on! Why are you wincing?! The math involved is multiplication and subtraction...

[AstrosFan]

PkI = PkR - PkHR*LWHR

I'm not wincing at the math. I'm wincing at phrases like PkI, PkR, PkHR, and LWHR. Do you just make these up for fun?

[SABR Matt]

I shorten things because if I didn't the equations would be hard to read.

Here's a decoder ring.

LWHR = The linear weight value of a home run
PkR = The park's impact on run scoring per game per team above average
PkHR = ditto but HR rate instead of run scoring.
PkI = ditto but run scoring not by long-ball