Xera Problems

[kyle972]

I have been trying to compute the Xera using Burnson's formula. I have been unable to match it to the xera numbers shown in the playerlink database. I also notcied that the Actual to Date and Last 31 Days xERA are not matching even though they list the same information such as innings etc. The Last 31 days covers the infomation in Actual to Date so shouldnt these match at this point in the season?


Could you please post the version of the xERA that you are using to calculate. I have checked and rechecked the formula posted in the glossary and read what threads there were on the issue but have been unable to get an xERA anywhere close to what is posted.

It is a complicated formula, but there is an error somewhere.

Thanks.

[RAY@HQ]

We're aware of the YTD/L31 issue.

I'll track down the current xERA formula. It's possible the glossary isn't up to date.

[Tom_T]

My Excel spreadsheet works for xERA, so let me give you what I have. It can be tricky to get the parentheses right, and you need to know where to use a percent rather than a fraction. These expressions are copied-and-pasted from Excel, and edited to replace cell references with the BPI acronyms:

xER% = 0.96 - 0.0284 * (GB/FB) ... where GB and FB are the raw numbers

xS% =((64.5+(Dom*1.2)-(Ctl*(Ctl+1))/20)+((0.0012*(GB%*GB%))-(0.001*GB%)-2.4))/100
... where GB% is expressed as a percent. e.g. Instead of .425, use 42.5.

BIP = (IP * 2.82) + H - K

xER = xER% *(FB/10) + ((1-xS%)*((0.3*BIP)+BB)) ... where FB is the raw number

xERA = (xER * 9) / IP

As an example, here are the results for Carlos Zambrano as of 5/1:

GB=56, LD=24, FB=37
xER% = 91.7%
xS% = 73.0%
BIP = 120
xER = 15.53
xERA = 3.43

Please note that the Last-31-Days xERA in Playerlink is the correct one, not the YTD figure. Right now, last-31 and YTD are the same number of innings, but now that we're into May, that will change -- I'm not sure if the xERA problem will go away then.

[RobR]

L31 vs YTD xERA should be sorted out beginning with tomorrow morning's stat run.