How do you calculate wOBA?
by Kirk on May 26, 2009 3:07 PM PDT
65 comments
I have seen this stat often on this site and I understand what it is and its purpose but what I don't know that I want to know is how to calculate it. I would love to be able to calculate it myself and I'm sure other people on the site would as well.
I found this explanation on how to calculate it but the way it is explained is a little over my head as it looks like how you would do it on an Excel spread sheet and I do not know how to use excel. If anyone can explain to me how to do it that would be great.
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wOBA is a similar calculation to tRA
there’s no real shorthand way to calculate either, since they are both the summations of individual results over the course of a season.
wOBA (without SB/CS factor)
0.72*uBB + .75*HBP + .9*single + 1.24*double + 1.56*triple + 1.95*homerun + .92*rboe
Out of curiosity, how would you factor SB/CS into wOBA?
Is that the light at the end of the tunnel, or the headlights of an oncoming train?
I wouldn't, and don't.
If you wanted to however, you’d need to come up with weights in the same manner as done to come up with the weights for the above events.
So wOBA treats all outs equally?
also, a little confused as to why your values differ from these linear weights
by seattlebruin on May 26, 2009 3:20 PM PDT up reply actions
Which you can find on a player's Baseball-Reference splits page
by Jeff Sullivan on May 26, 2009 3:42 PM PDT up reply actions
Thank you guys for the help.
I am sure you have answered this question many times before and I’m glad you answered it once more.
Why is reaching base on error worth more than a single?
Is it because you can get more than one base on an error?
Determined, Jonesing Commentor | Proud proprietor of Wyomingroutes.org & Washingtonhighways.org
Pretty much.
But there’s more to it. I’m going to have to let others explain it, though.
Fans are typically idiots.
by The Typical Idiot Fan on May 27, 2009 2:12 AM PDT up reply actions
SB/CS
wOBA at FanGraphs includes stolen bases and caught stealing. The values for SB/CS in the formula are always pretty close to .5 and .25 respectively.
by davidcameron on May 26, 2009 5:14 PM PDT up reply actions
Should be negative
A steal is about +0.25, while getting caught is about -0.50.
by Jeff Sullivan on May 26, 2009 10:21 PM PDT up reply actions
Has that changed?
I thought it was a 3 successful steal to 1 caught stealing ratio. Those numbers would make it a 2:1 ratio.
Fans are typically idiots.
by The Typical Idiot Fan on May 27, 2009 2:13 AM PDT up reply actions
2:1 would be neutral
you have to successfully swipe the third before you’ve positively contributed to run scoring.
by seattlebruin on May 27, 2009 8:07 AM PDT up reply actions
They're approximations
After doing some research, the true values as derived by Tango are closer to +0.2 and -0.47.
by Jeff Sullivan on May 27, 2009 9:38 AM PDT up reply actions
I have another StatCorner related question:
Why is Zack Greinke’s tRA+ 175, while his tRA is 1.29 and the league average is 5.06? 1.29/5.06 is 3.92, so why doesn’t he have a 392 tRA? Or am I way off base about how ERA is calculated?
From the Glossary
tRA+
Like wOBA+. tRA+ is equal to [((lgTRA – tRA) / lgTRA) + 1] * 100. This formula puts tRA+ on the same scale as wOBA+. A tRA+ of 150 represents that the pitcher’s tRA was 50% better than league average. A tRA+ of 75 means the pitcher’s tRA was 25% worse than average.
by Jeff Sullivan on May 27, 2009 1:03 PM PDT up reply actions
This might better be suited for the statistical analysis thread
but how do you convert tRA into runs?
St. Louis Cardinals... defying win expectancy since 2008
by vivaelpujols on May 27, 2009 8:19 PM PDT up reply actions
I mean
if you apply the coefficients on Graham’s primer to batted ball rates of players, how do you convert those to tRA?
St. Louis Cardinals... defying win expectancy since 2008
by vivaelpujols on May 27, 2009 8:20 PM PDT up reply actions
How far back have you gone in your tRA reading?
I’m pretty sure he explained this in a huge post sometime a while ago.
by Jeff Sullivan on May 27, 2009 8:49 PM PDT up reply actions
I read the tRA primer, but I couldn't find anything else on it on LL (besides the "no numbers" version)
It says the formula is tRA = expected_runs/expected_outs*27. I tried doing that and I got a “bad” number. Maybe I’m calculating xRuns and xOuts wrong. Is it just the out or run coefficients for each outcome, multiplied by the frequency, and then added all together?
St. Louis Cardinals... defying win expectancy since 2008
by vivaelpujols on May 27, 2009 9:27 PM PDT up reply actions
"Is it just the out or run coefficients for each outcome, multiplied by the frequency, and then added all together?"
Yes. If you’ll allow me a bit of a messy comment:
Call the overall total, expected runs, and expected outs of outcome [y], i_[y], r_[y] and o_[y] respectively.
xR is therefore i_[j]r_[j] summed over j=K, BB, HBP, etc (i.e. the tRA outcomes)
xO is therefore i_[j]o_[j] summed as above
tRA is then (xR/xO)*27
gotcha
thanks
St. Louis Cardinals... defying win expectancy since 2008
by vivaelpujols on May 27, 2009 10:32 PM PDT up reply actions
Can't you just weigh slugging and OBP to get a rough, non-steal wOBA?
St. Louis Cardinals... defying win expectancy since 2008
That's called GPA and THT has it. It's 1.8*OBP + SLG
But as Jeff says, why not use the better metric?
For reference, the comments of:
This.
...and now I'm here
GPA is a decent, off the top of your head, way to see which of two players is a better hitter
Obviously, you’d use wOBA whenever you have the chance, but if you just want a quick and dirty way to estimate players talent, you could use GPA.
St. Louis Cardinals... defying win expectancy since 2008
by vivaelpujols on May 27, 2009 8:19 PM PDT up reply actions
When is calculating GPA going to be easier than checking wOBA?
by Aaron Campeau on May 27, 2009 8:33 PM PDT up reply actions
/shrugs
St. Louis Cardinals... defying win expectancy since 2008
by vivaelpujols on May 27, 2009 8:43 PM PDT up reply actions
You are trapped on a desert island with the OBP and Slugging of every baseball player in a book?
Jose Lopez roxxorz my boxxorz.
51!
Not many scoreboards list OBP and SLG
by Jeff Sullivan on May 28, 2009 10:43 AM PDT up reply actions
I have a Dare
it doesn’t like StatCorner
by seattlebruin on May 28, 2009 12:04 PM PDT up reply actions
If someone gives me $20K
I’ll develop a mobile version of the site.
Wait since when does FanGraphs show wOBA?
by seattlebruin on May 28, 2009 1:14 PM PDT up reply actions
Also, FanGraphs won't let me search for players on my phone
by seattlebruin on May 28, 2009 1:15 PM PDT up reply actions
They've had it for a while.
SC wOBA is better but Fangraphs wOBA is close enough for the situation you’ve described.
by Aaron Campeau on May 28, 2009 1:45 PM PDT up reply actions
Still doesn't solve that the stupid Dare's browser gives me an error whenever I try to search for a player
says I’ve reached the character limit as soon as I type the first letter.
by seattlebruin on May 28, 2009 1:52 PM PDT up reply actions
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