A metric that determines how effective a fielder is (outfield or infield) at cutting off batted balls (fielding batted balls before they get behind the defense) hit to various areas of the field. The resulting value is an indication of how many runs a certain fielder has gained or lost for his team compared to what an "average" fielder would do on plays in the same area of the field.
To calculate RngR, we must break the baseball field into various zones (there are 64 zones used in the RngR formula). The percentage of batted balls cut off by fielders in the various zones is determined, and compared to the percentage of batted balls cut off in those zones by a particular player. We can then subtract the league average performance from a player's individual performance to yield that player's RngR. All the possible scenarios are analyzed to determine their run value, so the final RngR number is a net gain/loss of team runs.
As an example, let's use zone S, which is about halfway between first and second base. We'll say that of all groundballs hit into zone S, 25 percent of them are fielded by the second baseman. When we examine the data for a particular player, however, it turns out his percentage of groundballs fielded in zone S is 18 percent. Since he is performing below the league average, his RngR for this zone will be a negative number.