by gbrookes » Fri Jan 29, 2010 6:13 pm
I found a formula for ERP (not the same as NERP) os a link that was posted to one of the strategy postings on offense and defense. I simplified the formulas so that I could get something that I could use for managing strat teams, that was simple enough that I could actually use it day to day. It is BASED on ERP, but not technically or precisely the same as ERP. The article distinguished between NERP (an older theory of run production) and ERP (a more recent theory).
For what it's worth, my simplified version of the formula is:
ERP* (GB scale) = walks *1.2 + singles * 2 + doubles *3.6 +triples *5.4 + homeruns * 7.
This number result doesn't really correlate to any exact run prediction. It is just a scale that I use to compare one player to another - like using the Dow Jones to read the stock market change from day today. The absolute number doesn't really mean anything - only the change or difference means anything.
It doesn't work perfectly, but I find that a difference of 7 is roughly equivalent to a 1R or 1L effect in strat's balance ratings.
To the actual player card I add in the ballpark single and home run effects based on the park that we are playing in. For team management I default to the home ball park. For convenience, I add in the ballpark singles for both player and pitcher on the batter's cards, since most pitchers allow ballpark singles on their cards. If not, I adjust the pitcher's card accordingly. All in, a good player should have a rating of about 100.
As you can see, the relationship between singles, doubles, triples and HR's is not quite linear. To be honest, the ERP formula was kind of bizarre. This is what I got when I simplified it (with some simplifying assumptions). I do find that it works pretty well in game experience, as a predictor of what may happen, and for overall run production. (Base stealing, base running, GBA's, defense and other factors I just use my own judgement (and the fielding X chart summary) to adjust for).
Note - the main substantive difference between this formula and OPS is with respect to walks, and with respect to homeruns. My simplified ERP gives more weighting to walks and homeruns than does the OPS formula.
So, I AM happy with this ratings book, esp. since it is in spreadsheet format! I can enter the other data I need to to get my ERP calcs going, and saved!
Geoff