Pitching Runs
From Wiki
Pitching Runs is part of the Pete Palmer's Linear Weights System, serving as a measure of how many runs a pitcher has prevented compared to an average pitcher. Originally, Pitching Runs was calculated simply as the number of earned runs prevented:
PR = Lg(ER/IP)*IP - ER
In the ESPN Baseball Encyclopedia, a term dealing with unearned runs was added to the equation:
PR = Lg(ER/IP)*IP - ER + .5*(ER - R*Tm(ER/R))