Help with calculating WARP (from basketball-prospectus)

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JoshEngleman
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Re: Help with calculating WARP (from basketball-prospectus)

Post by JoshEngleman » Mon Feb 29, 2016 7:41 pm

Kevin Pelton wrote:LgOffRatMajor is just offensive rating -- same as LgOffRatMinor except offensive rebounds are subtracted out.
Thanks for the quick reply. I don't know what it is, but I'm still not seeing it. I've gotten to this point any everything is essentially the same (my LgOffRatMin has been slightly different. I have 91.3 instead of 91.45. Not sure why there's a difference, but that's probably not super important right now).

I have been assuming LgOffRatMinor = Lg.PC / Lg. Possessions * 100, which is 190275 / 208413 * 100 for me.

I have no doubt this is going to come off stupid, and I'm sure when this finally hits me, I'll look back and feel stupid, but I'm not sure what you mean by "offensive rebounds are subtracted out".

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Re: Help with calculating WARP (from basketball-prospectus)

Post by Kevin Pelton » Mon Feb 29, 2016 7:50 pm

So Minor is (100*PTS) / (FGA + (.44*FTA) + TO). Major is (100*PTS) / (FGA + (.44*FTA) - OR + TO).

Basically the logic is we're trying to figure out the ratio of points per possession (where an offensive rebound continues the possession) to points per play (where an offensive rebound begins a new play).

On the discrepancy in minor ratings -- are you including team turnovers? In my calculations, turnovers are the sum of player turnovers, which does not include a handful of things like 24-second violations.

JoshEngleman
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Re: Help with calculating WARP (from basketball-prospectus)

Post by JoshEngleman » Mon Feb 29, 2016 7:55 pm

Kevin Pelton wrote:So Minor is (100*PTS) / (FGA + (.44*FTA) + TO). Major is (100*PTS) / (FGA + (.44*FTA) - OR + TO).

Basically the logic is we're trying to figure out the ratio of points per possession (where an offensive rebound continues the possession) to points per play (where an offensive rebound begins a new play).

On the discrepancy in minor ratings -- are you including team turnovers? In my calculations, turnovers are the sum of player turnovers, which does not include a handful of things like 24-second violations.
Probably could have saved myself an hour or two by asking these questions earlier. I've got it now. I wasn't doing exactly that above, but apparently what I was doing was close. I've got it now (up to this point at least). Thanks so much for the quick responses. When I've got it completely finished, I'll probably write up a full example.

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