Thursday, March 22, 2012

Strike Zone Heat Maps (Baseball Mogul)

As I mentioned here, this is the year that Baseball Mogul went from being a random number generator (like Strat-O-Matic or previous computer sports games) to becoming a true physics-based simulation of each pitch. However, it's difficult to determine if our model is realistic without having a way to visualize the results. So, I added heat maps to Baseball Mogul 2013, plus the functionality to record data for every single pitch.

Ideally, we should see the same patterns in our data that we see in Major League Baseball. For example, we know from actual pitch data that BABIP (Batting Average on Balls In Play) varies by pitch location:
Heat map by Dave Allen
This heat map is for right-handed batters only, with a view from behind the catcher. Imagine the batter standing to the left of the strike zone.

As you can see, BABIP is slightly higher in the lower part of the strike zone, because low pitches lead to more ground balls, and ground balls turn into hits a bit more often than fly balls.

And, the "hot zone" for BABIP tilts. That is, on low pitches, the highest BABIP occurs just inside the middle of the plate. On higher pitches, this region is a bit farther away from the batter.

This prime hitting zone tilts at this angle because the sweet spot of the bat passes through the strike zone roughly along this line. With the bat (and arms) pivoting on the batter's shoulder, it's easier to reach the high outside corner with the heart of the bat than it is to reach the high inside corner. So, with Baseball Mogul, I modeled the bat moving through the strike zone, by assigning different coeffecients of restitution to each point on the bat. The coefficient of restitution (COR) reflects how quickly the ball comes off the bat at each spot. It can be represented as a parabolic function along the length of the hitting surface, with the COR peaking at the bat's sweet spot.

I hope I didn't lose you with the technical jargon. Simply put, once this COR model is added to the simulation, we should see results that look somewhat like real life. So here's the same heat map from one season of Baseball Mogul:

Heat map by Baseball Mogul 2013

I honestly didn't expect it would look that good. As with the first heat map, BABIP is highest from the middle of the plate down to the bottom edge. And, we see the same tilt: on low pitches, the batter is more likely to hit the ball solidly if it's over the inner half of the plate. As the pitch moves up in the strike zone, BABIP improves as the pitch moves toward the outer half.

Very cool. I'm really looking forward to using these heat maps to continue to dig into the new simulation engine.


christos732 said...

holy crap i can't wait for the new version... ill be checking back to everyday until i see it!

Josh said...

Does this also mean the severe reduction of HRs to right and right-center fields by right-handed hitters on inside pitches, especially in pitcher's parks?

Clay Dreslough said...

@Josh. Yes! Now you see why we needed to use physics instead of random numbers. A random number table doesn't know how hard it is to muscle an inside pitch for a homer to the opposite field.

Anonymous said...

I first bought the game many many years ago, and have bought probably 7 or 8 versions throughout the years. I stopped the last 3 or 4, but, you may have won me back with that heat map.

Anonymous said...

Very cool. Kinda reminds me of the Ted Williams strike zone in Cooperstown...

Anonymous said...

do these vary hitter to hitter? Like would 97 Vlad Guerrero be able to have a 300 babip on balls bouncing?

Mightyzug said...

I play the Colorado Rockies who play in the two worst hitters parks of all-time historically. One way I try to manage that it by maximizing the number of pitchers I carry, minimizing bench players. The other way is by loading up on EVERY available sinkerball pitcher. I WANT my sinkerballers to keep the ball low, will the new heat map skew their results from well placed pitches from ground outs into hits? Any hope that the new game version will begin to recognize that my pitchers are better than their stats, and will stop giving up outlier HRs on the road (as if they were back at Mile High/Coors)?

Anonymous said...

Yes, finally a down & in changeup will not be drilled to right field for a 435 ft. homerun by the 2nd baseman with a pwr rating of 66. All is right in the universe again :)

ip video surveillance said...

This is a great blog,I like this content it is very great and enlightening. I am sure that this content will be very much useful for individuals.
heat mapping