Welcome to Evolving-Hockey!


Please have a look around!
If you have any questions, please see the Glossary section for explanations of the various metrics found on the site and the References section for background on the methods used.
We can be reached on Twitter – @EvolvingWild – for any and all discussion about the information found here.

Thanks,
Josh & Luke















































































































See References for more information.





See References for more information.

Under Construction




























































Away Team

Home Team





About


Data acquired from NHL HTM source via Emmanuel Perry's Dry Scape R functions which can be found on his GitHub page

You can find us on Twitter @EvolvingWild

If you would like to help support the work we do, you can become a patron through our Patreon Page



Current Verions

Model Version Release Date
Expected Goals 1.0 06/07/18
Statistical Plus-Minus / Goals Above Replacement (Skaters) 1.1 09/04/18
Goals Above Replacement (Goalies) 1.0 09/04/18
Regularized Adjusted Plus-Minus (Skaters) 1.1 08/19/18
Regularized Adjusted Plus-Minus (Teams) 1.1 09/04/18
Penalty Goals (Skaters & Goalies) 1.0 07/04/18


Version History


Under Construction



© Evolving Hockey 2018. All Rights Reserved.

Glossary



General Terms:

Measure Definition
GF Goals For
GA Goals Against
SF Shots For (goals, shots on goal)
SA Shots Against (goals, shots on goal)
FF Fenwick For (goals, shots on goal, missed shots)
FA Fenwick Against (goals, shots on goal, missed shots)
CF Corsi For (goals, shots on goal, missed shots, blocked shots)
CA Corsi Against (goals, shots on goal, missed shots, blocked shots)
xGF Expected Goals For (total goal probability of all Fenwick shots)
xGA Expected Goals Against (total goal probability of all Fenwick shots)


Strength State Definition
EV Even-Strength (5v5, 4v4, 3v3)
PP Powerplay (5v4, 5v3, 4v3)
SH Shorthanded (4v5, 3v5, 3v4)


Measure Definition
SD Standard Deviation


Skater Stats - Standard:

Metric Definition
iSF Total individual shots on goal
iFF Total individual fenwick shots on goal
iCF Total individual corsi shots on goal
ixG Total individual expected goals
Sh_perc Shooting Percentage: G / iSF
F_Sh_perc Fenwick Shooting Percentage: G / iFF
xFSH_perc Expected Fenwick Shooting Percentage: ixG / iFF
iHF Total invidiual hits for
iHA Total individual hits against
GIVE Total giveaways
TAKE Total takeaways
iPENT2 Total 2-minute minor penalties taken - includes offsetting penalties
iPEND2 Total 2-minute minor penalties drawn - includes offsetting penalties
iPEND5 Total 5-minute major penalties taken - includes offsetting penalties
iPENT5 Total 5-minute major penalties drawn - includes offsetting penalties
FOW Total faceoffs won
FOL Total faceoffs lost
FO_diff Faceoff differential: FOW - FOL
TOI_GP Time on ice per game played
TOI_perc Percentage of available team minutes played: TOI / total team TOI
OZS Offensive zone starts
NZS Neutral zone starts
DZS Defensive zone starts
OZS_perc Percentage of total zone starts in the offensive zone: OZS / (OZS + NZS + DZS)
DZS_perc Percentage of total zone starts in the neutral zone: NZS / (OZS + NZS + DZS)
NZS_perc Percentage of total zone starts in the defensive zone: DZS / (OZS + NZS + DZS)
ZS_rate OZS / (OZS + DZS)


Goalie Stats - Standard:

Metric Definition
GA Goals Against
GA_ Goals Against (fenwick shots without location data removed)
SA Shots On Goal Against
FA Fenwick Shots Against
xGA Expected Goals Against
SV_perc Save Percentage: 1 - (GA / SA)
FSV_perc Fenwick Save Percentage: 1 - (GA_ / FA)
xFSV_perv Expected Fenwick Save Percentage: 1 - (xGA / FA)
d_FSV_perc FSV_perc - xFSV_perc
GSAA Goals Saved Above Average: (League SV_perc * SA) - GA
GSAx Goals Saved Above Expected: xGA - GA_


Penalty Goals:

Metric Definition
take_count Total penalties taken that resulted in a change of strength state
draw_count Total penalties drawn that resulted in a change of strength state
adj_take Total raw goal value of take_count
adj_draw Total raw goal value of draw_count
take_AA Penalties Taken Goals Above Average (inverted, per position): adj_take centered around the positional mean
draw_AA Penalties Drawn Goals Above Average (per position): adj_draw centered around the positional mean
pens take_AA + draw_AA


Goals Above Average & Replacement (Skaters):

Metric Definition
EVO_AA Even-Strength Offense Goals Above Average (per position)
EVD_AA Even-Strength Defense Goals Above Average (per position)
PPO_AA Powerplay Offense Goals Above Average (per position)
SHD_AA Shorthanded Defense Goals Above Average (per position)
take_AA Penalties Taken Goals Above Average (inverted, per position)
draw_AA Penalties Drawn Goals Above Average (per position)
EV_GAR Even-Strength Goals Above Replacement (Offense + Defense, per position)
PP_GAR Powerplay Offense Goals Above Replacement (per position)
SH_GAR Shorthanded Defense Goals Above Replacement (per position)
Pens_GAR Penalty Goals Above Replacement (Taken + Drawn,per position)


Replacement Level (Skaters):

Metric Definition
Even-Strength (EVO + EVD) Aggregate rate below average of all skaters outside the top 13 F or top 7 D per team per season ('07-'18)
Powerplay Offense Aggregate rate below average of all skaters outside the top 11 skaters per team per season (per position, '07-'18)
Shorthanded Defense Aggregate rate below average of all skaters outside the top 11 skaters per team per season (per position, '07-'18)
Penalties (Take + Draw) Aggregate rate below average of all skaters outside the top 13 F or top 7 D per team per season (all situations, '07-'18)


Goals Above Average & Replacement Minimum TOI Thresholds (Skaters):

Metric Definition
Even-Strength (EVO + EVD) 60 minutes
Powerplay Offense 25 minutes
Shorthanded Defense 25 minutes
Penalties (Take + Draw) None


Goals Above Average & Replacement (Goalies):

Metric Definition
GAA_per_fenwick Goals Above Average per Fenwick Shot Against (the transformed coefficient from the regression. See below)
FA Total fenwick shots against
GAA Goals Above Average: FA * GAA_per_fenwick
GAR Goals Above Replacement: GAA + (FA * 0.007312411) // inverted replacement level GAA_per_fenwick
WAR GAR / season goals per win


Goals to Wins Conversion:

  • Following the Pythagorean Expectation method (originally developed in baseball - explained here), we find the optimal x in the following equation:

    • W% = GFx / ( GFx + GAx )


  • This works out to a “pythagorean exponent” of ~2.1 (similar to prior work here and here). We use the following calculation per season to derive “goals per win”, which allows us convert skater and goalie GAR into WAR:

    • Goals Per Win = (4 * League GF per Game) / 2.091



Methods:

Relative to teammate (rel_TM):

  • player on-ice CF60 - weighted average of all teammates' on-ice CF60 (weighted by player TOI % with teammate)
  • This calculation is used for all respective rel_TM measures (GF, xGA, etc.)



Regularized Adjusted Plus-Minus (RAPM)

  • Shift-level weighted ridge regression. The target variable is a per 60 rate (separate regressions are performed using GF60, CF60, and xGF60 as the target variable), the weights are the length of each shift (shift is defined as a period of play where no player substitutions occur), and the predictor variables are:

    • all skaters - offense (dummy variable, 1 = on ice, 0 = not on ice)
    • all skaters - defense (dummy variable, 1 = on ice, 0 = not on ice)
    • all goalies - defense (dummy variable, 1 = on ice, 0 = not on ice). Only used in GF60 regression
    • score state (7-level factor variable, home lead of -3 through +3)
    • strength state (factor variable equal to the applicable strength states in the regression)
    • offensive “zone start” (1 = shift included at least one faceoff in the offensive zone, 0 = no faceoff in offensive zone)
    • defensive “zone start” (1 = shift included at least one faceoff in the defensive zone, 0 = no faceoff in defensive zone)
    • back-to-back (1 = offensive team had one night of rest, 0 = offensive team had more than one night of rest)


  • The skater ratings are the coefficients that result from the regression. These are interpreted as a skater's offensive and defensive contribution (per 60 minutes) to the league scoring rate (Goals, xG, or Corsi).



Goalie GAR/WAR

  • Fenwick shot-level regularized logistic regression. The target variable is 1 (Goal) or 0 (No Goal) and the predictor variables are:

    • all shooters (dummy variable, 1 = skater took the shot, 0 = skater did not take the shot)
    • all goalies (dummy variable, 1 = goalie facing the shot, 0 = goalie not facing the shot)
    • expected goal value of the fenwick shot (probability between 0 and 1)
    • strength state (8-level factor variable: 5v5, 4v4, 3v3, 5v4, 5v3, 4v3, Ev5, Ev4)
    • shooter score state (3-level factor variable: shooter team is leading, tied, or trailing when shot was taken)
    • shooter venue (home or away team)
    • shooter position (forward or defenseman)
    • back-to-back (home team / away team playing with < 2 nights of rest)


  • The goalie coefficients that result from this regression are interpreted as each goalie's impact on the odds of a goal being scored. These coefficients are converted to probabilities and multiplied by the total fenwick shots each goalie faced to arrive at “Goals Above Average” (GAA).
  • Goals Above Average is then converted to Goals Above Replacement (GAR) as such:
    • GAA + (FA * replacement level GAA per fenwick)



Shooter GAR

  • The shooter coefficients from the regression described in the Goalie GAR/WAR section.
  • The shooter coefficients that result from this regression are interpreted as each shooter's impact on the odds of a goal being scored. These coefficients are converted to probabilities and multiplied by the total fenwick shots each shooter took to arrive at “Goals Above Average” (GAA).
  • Goals Above Average is then converted to Goals Above Replacement (GAR) as such (replacement level is set per forward and per defenseman using the same cutoff described in the Replacement Level (Skaters) section):
    • GAA + (iFF * replacement level GAA per fenwick)



Table types

  • Rate: per 60 minutes of play, calculated as: (raw metric / TOI) * 60
  • Impact: implied total, calculated as: (per 60 metric / 60) * TOI
    • The relative to teammate and RAPM metrics are inherently per 60 rate stats - this is used to “convert” the rates into counting stats



Score Adjustments

All on-ice and relative to teammate metrics (EV, PP & SH - Skaters and Teams) are score adjusted using the method developed by Micah Blake McCurdy.


Even-Strength


Goals:

Home Score State Home Weight Away Weight
Trailing 0.936 1.074
Tied 0.948 1.058
Leading 0.987 1.014


Expected Goals:

Home Score State Home Weight Away Weight
Trailing 0.915 1.103
Tied 0.951 1.055
Leading 0.992 1.008


Shots on Goal:

Home Lead State Home Weight Away Weight
-3 or worse 0.861 1.193
-2 0.892 1.137
-1 0.916 1.101
0 0.973 1.029
+1 1.036 0.967
+2 1.072 0.937
+3 or better 1.103 0.915


Fenwick Shots:

Home Lead State Home Weight Away Weight
-3 or worse 0.860 1.193
-2 0.885 1.150
-1 0.911 1.109
0 0.970 1.032
+1 1.036 0.966
+2 1.074 0.935
+3 or better 1.109 0.911


Corsi Shots:

Home Lead State Home Weight Away Weight
-3 or worse 0.844 1.227
-2 0.869 1.177
-1 0.900 1.124
0 0.971 1.031
+1 1.051 0.954
+2 1.100 0.917
+3 or better 1.139 0.892



Powerplay / Shorthanded ***


Goals:

Home Score State Home Weight Away Weight
Trailing 0.860 1.194
Tied 0.928 1.084
Leading 0.980 1.020


Expected Goals:

Home Score State Home Weight Away Weight
Trailing 0.843 1.230
Tied 0.915 1.102
Leading 0.995 1.005


Shots on Goal:

Home Score State Home Weight Away Weight
Trailing 0.841 1.234
Tied 0.930 1.082
Leading 1.041 0.962


Fenwick Shots:

Home Score State Home Weight Away Weight
Trailing 0.838 1.239
Tied 0.926 1.086
Leading 1.031 0.971


Corsi Shots:

Home Score State Home Weight Away Weight
Trailing 0.837 1.241
Tied 0.930 1.082
Leading 1.045 0.959

*** Home & Away weights are reversed for shorthanded goals, xG, shots, fenwick, and corsi against



Penalty Goals

Home Score State Home Weight Away Weight
Trailing 1.175 0.870
Tied 1.049 0.956
Leading 0.964 1.039




© Evolving Hockey 2018. All Rights Reserved.


Loading...