tRAr and wOBAr

I have been working on these two stats for awhile now, along with overhauling StatCorner and while the latter has stalled a bit with a personal time crunch, the new stats have been ready and I'm finally at the point where I wanted to at least get them out there in the wild. There will be much more detailed explanations of both of these forthcoming.

tRAr is basically what tRA* was intended to be. It takes each of the inputs to tRA (GB, FB, LD, IF, Bt, K, BB, HBP, HR) and regresses them first toward the pitcher's recent (max three year) historical rates and then factors in the league average if that 3-year sample is too small.

wOBAr is geared toward the same goal, but is different in a way that builds more off of PrOPS than wOBA itself. PrOPS took a player's batted ball rates and used the league average rates of hits on each type to come up with a modified OPS for the hitter, a way to spot check if someone was getting unlucky on their batted balls. What wOBAr does is take that basic concept and, like tRAr, use the player's own recent past as the baseline, filling in league rates only if needed.

In other words, say Player X hit 100 fly balls in 2009, and 300 over 2007-9 combined. Over those 300, 15 have gone for singles, 30 for doubles, 0 for a triple and five for a home run. The league average would say that 17 of those would go for a single, 24 for a double, three for a triple and three for a home run. Based on how meaningful a sample of 300 is, a mix of the player and league rates is used to come up with regressed rates for 1B, 2B, 3B and HRs for those 100 fly balls in 2009. Repeat across all batted ball types and then you can add up all the singles, all the doubles, etc and end up with the inputs to wOBA.

Both of these are available on the redesigned (and not fully done redesigning, so suggestions welcome, but holier-than-though critiques are not) player pages on StatCorner, such as RRS and Ichiro! Both of these might have some coding bugs in them so I would not yet go around treating them as gospel. The point is to get the idea out there.

Important note:

Because I currently only have three years of data for this to run against, the earlier year (2007, even 2008) of tRAr and wOBAr are not going to be great because they end up getting heavily regressed.

For instance, estimating Erik Bedard’s 2007, the formula wants to look at his 2004-7 data in order to figure out his recent rates. But I don’t have 2004-6 data, so it ends up only using 2007, which means his sample size is small, which means he (like everyone else) gets heavily regressed toward league average.

I’m still working on getting past retrosheet years into my new DB schema. Once I do that, then those earlier years will be more meaningful.

 

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