Friday, July 13, 2012

Improving Basim and feedback

I'm working on improving Basim and eWAR (some new content and some bug fixes), but it's going to take time to run the new calculations.  (I'm also going to run them on more data points, i.e. multiple seasons.)  While that happens, is there anything you think it would be cool for me to research/write about?  Is there any improvement you'd suggest to Basim?  Anything whose value in time and dollars I should compare to voting and donating to a campaign?  If so, leave suggestions here in the comments (or drop me an email).

Also, I've spent a lot of time trying to decide how to integrate into eWAR the fact that lineups aren't totally irrelevant; my new approach is to take an average lineup (i.e. average 1st hitter, average 2nd hitter, etc.), and look at the run differential between replacing a test player for a given slot and replacing the league average player for that slot; this approach isn't perfect, though, because it is at risk of delegating all less than average players to ninth so that they total plate appearances in which they're batting, relative to the league average player, is minimized (and shove all better than average players to leadoff).  Suggestions?

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  1. Reading through Basim, a sort of weird idea occurred to me: does batting utility in a lineup add linearly between players?

    Imagine a game called Simpleball, where each team only has one batter and all the running is done by substitutes. If batter A is normally worth 1/9 of a run above replacement per game, one might naively expect his Simpleball team would generally score 1 run above replacement.

    However, imagine that batter A has a perfect batting percentage, and through dark magic always gets exactly a single. If batter A was on the Red Sox, he'd be a great player and worth lots of runs above replacement, but the Red Sox would still score a finite number of runs. However, batter A's Simpleball team would score infinity runs in every game. Similarly, a lineup composed of 9 clones of batter A would score infinity runs in every game.

    So from this rather silly example, we see that the utility of batters in a lineup tends to add in a nonlinear way; in specific if you already have a good lineup you probably get more utility out of making it better, and you probably also get more utility out of spreading out your lineup's goodness than concentrating it in a few players (this is a guess based on intuition).

    Is this nonlinear element large for typical baseball lineups? I'd think that it would be, but it'd be interesting to investigate the matter. If nothing else, it has a lot of implications for trading, since it makes trades between teams a non-zero sum game even from a batting perspective.

    1. You're totally right--runs don't add linearly; WAR attempts to correct for this, I believe, but eWAR doesn't yet. Come to think of it, it wouldn't be that hard to do some simulations and see how non-linear it is; maybe I'll do that soon. And yup, this is a possible case of non-zero-sum trades, which actually bears some resemblance to the point made by Matt Yglesias that players are worth more to big-market teams than small market ones: