Earlier this week, Jeff Fletcher did something that endeared him to me. He put up a poor piece of data analysis. Why is that endearing? Well, I am an advocate of doing poor data analysis, or at least doing it with the right attitude. It’s not just that I am an author of many a hasty and incomplete piece of analysis, though that is surely true. I think that even a simple look at data, can help set up a discussion that is clearer and more intelligent. I also don’t think journalists should be afraid of being FJM’d every time they want to fire up Excel.

Let’s talk about Fletcher’s work, and then see the analysis can be improved in a way that still falls short of writing a thesis. What he did was look at the top twenty and bottom twenty players, as sorted by the percentage of first pitches swung at. What he found was that, as judged by OPS, the more aggressive players were the better hitters.

This result does not really surprise me. Power hitters should be a little more aggressive than non-power hitters (the value of contact is relatively higher for them), and OPS tends to overrate slugging percentage. The twenty most aggressive hitters should consist of more power hitters than the twenty least aggressive hitters. Those hitters will have a higher slugging percentage, and are therefore more likely to have a higher OPS.

We can make some quick improvements on Fletcher’s preliminary work. First, we’re going to use the whole data set, and not just forty players at the extreme ends of a distribution. Second, we’re going to use wOBA (the Fangraphs variety) so that we don’t overweight slugging percentage. Third, we’re going to use percentage of all pitches swung at, as a more comprehensive measure of plate discipline.

Here’s what the whole dataset looks like:

Swing Percentage has a slight negative correlation with offensive value

You can see another aspect of this data that lead Fletcher astray. There aren’t many players out on the extremes of the swing percentage distribution, and those players are a pretty weird group. The players with extreme approaches also tend to be slightly worse hitters than players with more normal plate discipline. So Fletcher’s top 20, bottom 20 are probably a poor guide to what makes sense for the typical player. If you want to know what the overall trend is, you can draw a least fit line through the dots. That will tell whether or not swing percentage has a generally positive effect on wOBA. A Lowess (locally fitted) line works similarly, but allows that a swing% far from average will have a different effect on wOBA than a swing% close to average. Generally, More Disciplined Hitters are Slightly Better Hitters

The correlation between selectiveness and hitting results isn’t terribly strong. Being predictable is probably the main thing a hitter wants to avoid. The local fitted line does a better job of reflecting the fact that very passive hitters are not as good as hitters with a more typical plate approach. The same holds true for very aggressive hitters.

If that’s not clear enough let’s break our hitters into four categories, based on their swing percentages. These categories are less fine grained than the analysis based on the scatterplot, but they have their own story to tell.

Again, taking a pitch clearly not hurting the guys in the more disciplined categories.

Why are we talking about this?

Fletcher’s post stemmed from some of Hank Schulman’s attempts to defend the Giants’ front office from accusations that they neglect plate discipline. Schulman says that the Giants believe that a hitter should be aggressive on good pitches. That is entirely correct. Half of plate discipline is, after all, to swing at the right pitches. However, I feel like the Giants use talk like this as a gloss for an organizational weakness. Every time the Giants staff talks about hitting philosophy, it seems like they are going on a about the evils of an overly passive approach. To hear them talk, you’d that they faced a daily battle to convince a reluctant group of players to occasionally swing the bat.

That sort of stuff makes me wonder. Does the front office understand that poor plate discipline is big part of the reason why the Giants are consistently amongst the poorest offenses in the NL? Either they do, and are making excuses, or they don’t, and are enthusiastically taking their team in the wrong direction.