Written By: Forrest Allen and Natalie Hansen

6-4-3 Charts recently introduced weighted heatmaps in the Synergy Tile on the 643 interface, giving coaches a revolutionary way to analyze the relationship between pitch location and outcome. Weighted Heatmaps are now available for all 643 + Synergy baseball and softball users. This blog will compare weighted heatmaps with traditional heatmaps, explain how we developed weighted heatmaps, and discuss how weighted heatmaps can be interpreted and utilized by coaches.

Standard 643 Heatmaps:

Heatmaps bring together location and frequency of pitches in an intuitive visualization. The standard heatmaps available in the 643 Synergy Tile are shown with red indicating where the most pitches were thrown while blue areas show the areas with the least number of pitches thrown. Among their benefits, heatmaps can help uncover pitcher tendencies. The standard 643 heatmaps can be filtered to show whiffs, damage, and other outcomes based on pitch frequency and location. But pitch frequency is only a part of the story. It doesn’t tell us what happened on the pitch. Was it a whiff? Was it a rocket off the bat? What was the outcome?

Here’s where weighted heatmaps come to play.

Weighted Heatmaps:

Weighted heatmaps help tell a more complete story. Rather than telling us how often something occurs, weighted heatmaps quantify the impact of what happened on pitches thrown in those areas. The user can clearly see where good outcomes and bad outcomes occur. Rather than being colored based on pitch frequency, the 643 Weighted Heatmaps are colored based on outcome. Increases in run expectancy and the most damage happens in the darkest red while minimal damage occurs where the heatmap shows the darkest blue.

The Nitty Gritty:

Diamond sports are driven by an attempt to score runs for your own team and prevent runs by the opposing team. Ultimately, runs determine game outcomes. To create weighted heatmaps, we quantify the outcome of the pitch based on the changes in the run expectancy (RE) matrix. The RE288 matrix calculates the number of runs scored in each of the possible 288 game states (12 possible counts x 8 possible base states x 3 possible outs) and divides those runs scored by the number of occurrences for any given period. Think- ‘how many runs have scored before the inning ends after a 2-1 count, no outs, and runners on first and second?’

At the beginning of each inning, the 2023 D1 Baseball run environment has produced 0.766 runs; a game state of 0 balls, 0 strikes, 0 outs, and no runners on. As you would expect, balls and runners on base cause run expectancy to increase while strikes and outs cause run expectancy to decrease.

Picture this: a team leads off the inning with a double on the first pitch. Suddenly the game state goes from:

0-0 count with no runners on and no outs (.766 RE)


0-0 count with a runner on 2nd and no outs (1.974 RE)

With just one swing, the run expectancy shifted from .766 to 1.974. This change in run expectancy is how we quantify the outcome of each pitch. In this case, the pitch is assigned a value of 1.21; the increase in run expectancy from the pitch resulting in the double. This point would be displayed as red because of the damage caused by double.

On the other end of the spectrum, an out made on the first pitch of the inning would be assigned a value of -0.3642 as the run expectancy went from:

0-0 count with no runners on and no outs (.766 RE)


0-0 count with no runners on and 1 out (.4024 RE)

The savvy reader will notice how much bigger the impact of a double (1.2) is than an out (-.36). For every double given up on a pitch in that location, a pitcher would need to record 3 outs from pitches in that same location to bring that location back to neutral. But in the context of strikes, it’d take 15 to bring it back to neutral. This feature of our weighted heatmap make it very useful for creating specific areas of focus for coaches, and can be the beginning of a very fruitful analysis.

These individual pitches and their respective changes to run expectancy are plotted on the heatmap. The ‘weighted’ in weighted heatmap indicates the magnitude of the damage done or avoided of a pitch. This damage, or lack thereof, is summed for all the pitches in each location. The resulting total is what produces the colors across the plot.

In the 643 Charts Weighted Heatmap tab in the Synergy Tile, users have the ability to toggle between seeing the individual points overlaid on the weighted heatmap. Below we see two examples of the same heatmap with the points toggled on and off.

Seeing the individual pitches in the context of the shaded areas helps tell the story of the area; was there one major event that caused lots of damage but otherwise ok? Or, were there lots of events with smaller impacts to run expectancy? The weighted heatmaps show where a pitcher (or hitter) has their best and worst outcomes, in terms of changes in run expectancy.

How To Interpret Weighted Heatmaps:

Sure, weighted heatmaps help visualize outcomes, but how can we interpret them? How do we come to actionable conclusions?

Regardless of whether you are looking at a hitter’s or a pitcher’s weighted heatmap, the coloring scheme remains the same: 

  • Red indicates favorable outcomes for the hitter (hits/damage, balls, walks, etc.)
  • Blue indicates unfavorable outcomes for the hitter (outs, strikes, strikeouts, etc.)

Analyzing Weighted Heatmaps for Hitters

When analyzing a heatmap for a given hitter, the red indicates where they get hits, do damage, draws walks, etc. The blue indicates where the hitter whiffs, hits into outs, etc. The red areas inside the zone can indicate where a hitter mashes while the red areas outside the zone can indicate where the hitter draws balls. When formulating a game plan against a given hitter, pitchers should think “throw it to the blue” where the hitter tends to struggle.

Analyzing Weighted Heatmaps for Pitchers

When analyzing a heatmap for a given pitcher, the red indicates where hitters do damage off of them or where the pitcher misses with balls. For pitcher development purposes, the red can draw attention to areas for improvement. The blue indicates where they generate whiffs, get outs, etc. 

In the most simple terms, pitchers want to attack the blue, and hitters want to hunt the red areas of their respective weighted heatmaps.

Utilizing Filters

We’ve added several filters within the weighted heatmaps tab for more granular data analysis. Easily toggle handedness, date, and pitch types to explore specific questions. How has this pitcher performed against right-handed hitters with their fastball this season? Simply select RHH, date range, and fastball on the drop down to view the weighted heatmap for this criteria.

A Piece of the Puzzle

Weighted heatmaps serve as a great first stop when analyzing pitchers and hitters because they give an overarching view. They allow us to easily see where in the zone a player has good and bad outcomes. When putting together a specific game plan, coaches can compare heatmaps for a given pitcher to a heatmap of a given hitter to formulate their pitch calling plan. If you notice that a hitter struggles against fastballs busted up and in, and your pitcher excels in this area, you can begin to formulate specific plans for this matchup. Repeating this process across various pitch types and hitters can help coaches prepare for upcoming opponents.

Furthermore, see a hotspot in weighted heatmaps and want to know what happened on pitches in that area? Easily hop over to the Pitch Highlighter tab in the Synergy Tile and box select the zone of interest to view associated video.

In the future, 643 Charts plans to roll out more enhancements to the weighted heatmaps in the Synergy Tile to further aid coaches in scouting and player development. One enhancement  would be the ability to see specific pitchers vs specific hitters overlaid on the same plot to get more matchup specific insights. Additionally, the same process of assigning pitches scores for weighted heatmaps could also be applied to generate a leaderboard. Such a leaderboard would show which pitchers have the most effective [fastball, curveball, etc.] for a given time period. 643 Charts is excited to continue expanding features within the 643 Interface and Synergy Tile.