FORMULA
 
 The Player Impact Rating (PIR) is based on events which take place on the 
 field. Each event influences the outcome of the game in either a positive or 
 negative way. The player, his/her position, the event and the significance of
 the event all impacts the rating. Only those events which are statistically 
 listed on a team's web page are used.
 
 There are currently 11 events:
 * Goal scored
 * Missed shot on goal
 * Missed shot not on goal
 * Assist
 * Ground ball
 * Turnover
 * Caused Turnover
 * Faceoff won
 * Faceoff lost
 * Goal saved
 * Goal allowed
 
 There are six statistically segregated positions:
 * Attack
 * Midfield (offensive or undetermined)
 * Midfield (defensive or long stick)
 * Midfield (faceoff)
 * Defense
 * Goalie
 
 The Player Impact Rating formula is as follows:
 
 PIQ =   C01 * goals scored          
        -C02 * missed shots on goal    
        -C03 * missed shots off goal 
        +C04 * assists                        
        +C05 * ground balls           
        -C06 * turnovers              
        +C07 * caused turnovers       
        +C08 * faceoffs won                    
        -C09 * faceoffs lost          
        +C10 * goals saved                 
        -C11 * goals allowed          
 
 where: C01, C02, C03, C04, C05, C06, C07, C08, C09, C10 and C11 are weight 
 coefficients modulating the signiificance of each event. These coefficients
 change for the six positions.
 
 goals                 c01 =  1.00
 shots                 c02 = -0.10
 shots missed off goal c03 = -0.05
 assists               c04 =  1.25
 ground balls          c05 =  0.45
 turnovers             c06 = -0.6
 caused turnovers      c07 =  1.0
 faceoffs won          c08 =  0.225
 faceoffs lost         c09 = -0.225
 goals saved           c10 =  0.80
 goals allowed         c11 = -0.80
 
 If shots on goal data is unavailable, c02 =-0.15 and c03 = 0.0.
 
 Defense factor indicates goals allowed compared to opponent's goals scored
 per game. It measures the performance a a team in holding under their
 normal goal production. Range from 0.5 to 1.0.
 
 Offense factor indicates goals scored compared to goals allowed by an
 oppoent per game. It measures the performance of a team in score goals
 in excess of an opponent's team goal allowance. Range from 0.5 to 1.0,
 
 Opponent's Strength based on strength of schedule of a team.
 Range from 0.5 to 1.0
 
 The normalized PER is as follows
 
 attack:   PER (normalized 1) = PER * OFF * SOS
 midfield: PER (normalized 1) = PER * (OFF+DEF)/2. * SOS
 defense:  PER (normalized 1) = PER * DEF * SOS
 goalie:   PER (normalized 1) = PER * DEF * SOS
 
 Finally, impact ratings are normalized to a maximum of 100.