F/X VisualizationsApril 07, 2009
Saying Goodbye
By Dave Allen

I know this post is supposed to be about opening day, but there was one more thing I wanted to do before turning my attention to the current season. Peter Jensen's amazing series on using the Gameday data to build a fielding metric prompted me to get that data and play around with it. The first thing I wanted to do was make a run value by hit location map. It seems only right to present such images for the two closed New York parks as a way of saying goodbye before really getting into the new season.


I used Jensen's hit factors to translate gameday's pixel into feet, so the two images should be to scale. The run value should include all hits, outs, foul outs and HRs since 2005.


I don't care what your fancy colored squares say - sac bunts and grounders to the right side are just as important as those home runs! Why don't you just make a Lite Brite the manager of a ball team, huh?

I'm Murray Chass and I approved this message.

Dave, fantastic. One request please: show those maps based on the handedness of the batter (or even batter/pitcher).

Ideally, we should see the red blobs shifted over, with patches of green more clearly separating them.

Great news that Murray Chase is a reader!

Good idea Tango, here is Shea separated by handedness of batter (not batter/pitcher).


Hey Dave, I know you've gotten comments about your graph colors, but do you mind if I make one more? I have no problem with the ROYGBIV color scheme--in fact, I think it's the way to go--but to me your color scale is backward. Red is "hot" and ought to be the highest number, while blue/violet is "cold" and ought to be the lowest number.

And on a visceral level, I have a hard time interpreting a graphic where a home run is blue instead of red, know what I mean?



Yeah I do, a home run does seem more 'red' than 'blue' to me. But at the same time, negative numbers seem 'red' to me and positive numbers seem 'blue-green' to me. Like when the Dow Jones closes down it is reported in red and when it is up in green. I think that is what I thought when I made the original pitch location run value images.

I am just hypothesizing at this point but it seems to me when the scale is all positive blue in zero and red is high. But when the scale goes from negative to positive, then it flips and red becomes negative and blue positive. I don't know if that is generally the case or what, but that is kind of how it is in my head.

I definitely understand where you are coming from.

Well, no matter what color scheme you use, I enjoy your work, Dave. It's awesome.

Awesome work, David! Looking forward to your next post.

Dave, that works on Wall Street because red is the official color of a negative bottom line, and green is the color of money. More importantly, those are two-tone situations. Even market maps, like this one...


...just use two colors.

In general, ROYGBIV is best interpreted as "hot to cold", which is equivalent to "more to less."

Changing that relationship because a scale happens to go into the negative zone undermines easy interpretation of your graphs. There is nothing special about negative numbers in this case (or in most cases, really). They're just part of a scale. In fact, you could change your linear weights to a base of zero, with no negatives, and still get the same graphical result.

If you really think that the important distinction here is between positive and negative numbers, rather than relative position on a scale, then I'd recommend you just use two colors, as in the market map.