Pitching Stats 6: ERA+

This one may prove to be tricky, if only because there are a couple of ways to calculate it.  Baseball-Reference says they calculate it one way, Wikipedia says that bb-ref used to calculate it that way, but then they changed.  So, we may see some variation here.  Frankly, I’m not even sure why I’d want to use this counter-intuitive + stat anyway.  However, it’s in the game, and I’d like to be able to use it as a sanity check if nothing else.

Here’s the first way I am going to try it.  Defined by Wikipedia as the way bb-ref currently does the calculation:

ERA+ = 100 * (2 - (ERA/lgERA) * 1/ParkFactor)

No additional joins are needed for this, so we can just plug it in.  Let’s do it and check our results.

Awful.  Just awful.  1/3 of the result set was hugely off, and only about half was within 5 percent.

We’ll try the original recipe for this stat and see if we get better luck.  That one is:

ERA+ = 100 * (lgERA/ERA) * ParkFactor

And the results:

Much, much better.  24 within 5 points and only 1 more than 10.  And that one is also one that was way off on the first try.  I am good to keep this version and even to use it for evaluative purposes.  I think the difference between this and the game is probably down to park factors.  Here’s the CalcPitching table to this point:

DROP TABLE IF EXISTS CalcPitching;
CREATE TABLE IF NOT EXISTS CalcPitching AS

SELECT
    i.player_id
    , i.year
    , i.stint
    , i.team_id
    , i.league_id
    , r.sub_league_id
    , split_id
    , i.ip
    , i.ab
    , i.tb
    , i.ha
    , i.k
    , i.bf
    , i.rs
    , i.bb
    , i.r
    , i.er
    , i.gb
    , i.fb
    , i.pi
    , i.ipf
    , i.g
    , i.gs
    , i.w
    , i.l
    , i.s
    , i.sa
    , i.da
    , i.sh
    , i.sf
    , i.ta
    , i.hra
    , i.bk
    , i.ci
    , i.iw
    , i.wp
    , i.hp
    , i.gf
    , i.dp
    , i.qs
    , i.svo
    , i.bs
    , i.ra
    , i.cg
    , i.sho
    , i.sb
    , i.cs
    , i.hld
    , i.ir
    , i.irs
    , i.wpa
    , i.li
    , i.outs
    , i.war
    , @InnPitch := ((3*ip)+ipf)/3 AS InnPitch
    , round((9*i.k)/@InnPitch,1) AS 'k9'
    , round((9*i.bb)/@InnPitch,1) AS 'bb9'
    , round((9*i.hra)/@InnPitch,1) AS 'HR9'
    , round((i.bb+i.ha)/@InnPitch,2) AS WHIP
    , round(i.k/i.bb,2) AS 'K/BB'
    , i.gb/i.fb AS 'gb/fb'
    , round((i.ha-i.hra)/(i.ab-i.k-i.hra-i.sh+i.sf),3) AS BABIP
    , @ERA := round((i.er/@InnPitch)*9,2) AS ERA
    , round(((13*i.hra)+(3*(i.bb+i.hp))-(2*i.k))/@InnPitch+f.FIPConstant,2) AS FIP 
    , round(((13*(i.fb*f.hr_fb_pct))+(3*(i.bb+i.hp))-(2*i.k))/@InnPitch+f.FIPConstant,2) AS xFIP
    , round(100*((@ERA + (@ERA - @ERA*(p.avg)))/slg.slgERA),0) AS ERAminus
    , round(100*(slg.slgERA/@ERA)*p.avg,0) AS ERAplus
    
    FROM players_career_pitching_stats AS i
    INNER JOIN team_relations AS r ON i.team_id=r.team_id AND i.league_id=r.league_id
    INNER JOIN FIPConstant AS f ON i.year=f.year AND i.league_id=f.league_id
    INNER JOIN sub_league_history_pitching AS slg ON i.year=slg.year AND i.league_id=slg.league_id AND r.sub_league_id=slg.sub_league_id
    INNER JOIN teams AS t ON i.team_id=t.team_id
    INNER JOIN parks AS p ON t.park_id=p.park_id
WHERE i.split_id=1 AND i.league_id<>0;