module AgbHandicap

Constants

SCORING_SCHEMES

Public Class Methods

calculate(score, distances, rounded = true) click to toggle source

Calculate AGB score handicap as per David Lane's original algorithm

Example:

>> distances = [
     {'range_in_meters' => 91.44, 'total_shots' => 72, 'target_diameter_cm' => 122, 'scoring_scheme' => 'IMPERIAL'},
     {'range_in_meters' => 73.152, 'total_shots' => 48, 'target_diameter_cm' => 122, 'scoring_scheme' => 'IMPERIAL'},
     {'range_in_meters' => 54.864, 'total_shots' => 24, 'target_diameter_cm' => 122, 'scoring_scheme' => 'IMPERIAL'}
   ]
>> score = 1105

>> result = AgbHandicap.calculate(score, distances)

# File lib/agb_handicap.rb, line 27
def calculate(score, distances, rounded = true)
  result = agbhandicap(score, distances)
  rounded ? result.ceil.to_i : result
end

Private Class Methods

agbhandicap(score, distances) click to toggle source

# File lib/agb_handicap.rb, line 34
def agbhandicap(score, distances)
  rtrange = 32.0
  hc = 50.0

  while (rtrange > 0.01)
    nextscore = agbscore(hc, distances)

    if (score < nextscore)
      hc = hc + rtrange
    end

    if (score > nextscore)
      hc = hc - rtrange
    end

    rtrange = rtrange / 2
  end

  hc = 0 if (hc < 0)
  hc = 100 if (hc > 100)

  return hc.to_f.round(1)
end

agbscore(h, distances) click to toggle source

# File lib/agb_handicap.rb, line 58
def agbscore(h, distances)
  score = 0.0
  distances.each do | d |
    score = score + calculate_distance_score(d, h)
  end
  score
end

calculate_distance_score(distance, h) click to toggle source

# File lib/agb_handicap.rb, line 66
def calculate_distance_score(distance, h)
  range = distance['range_in_meters'].to_f
  shots = distance['total_shots'].to_f
  diameter = distance['target_diameter_cm'].to_f
  scoring = distance['scoring_scheme']

  score = 0
  sr = score_range(h.to_f, range).to_f

  case scoring
  when 'METRIC'
    score = 10
    (1..10).each do | n |
      score = score - solution((n.to_f * diameter / 20.0 + 0.357), sr)
    end
  when 'IMPERIAL'
    score = 9
    (1..4).each do | n |
      score = score - (2.0 * solution((n.to_f * diameter / 10.0 + 0.357), sr))
    end
    score = score - solution((diameter / 2 + 0.357), sr)
  when 'ONE_TO_FIVE' # could be worcester or NFAA round etc
    score = 5
    (1..5).each do | n |
      score = score - solution((n.to_f * diameter / 10.0 + 0.357), sr)
    end
  when 'INNER_TEN'
    score = 10
    score = score - solution((diameter / 40 + 0.357), sr)
    (2..10).each do | n |
      score  = score - solution((n.to_f * diameter / 20 + 0.357), sr)
    end
  when 'TRIPLE'
    score = 10
    (1..4).each do | n |
      score = score - solution((n.to_f * diameter / 20 + 0.357), sr)
    end
    score = score - (6 * solution((5 * diameter / 20 + 0.357), sr))
  when 'TRIPLE_INNER_TEN'
    score = 10
    score = score - solution((diameter / 40 + 0.357), sr)
    (2..4).each do | n |
      score = score - solution((n.to_f * diameter / 20 + 0.357), sr)
    end
    score = score - (6 * solution((5 * diameter / 20 + 0.357), sr))
  when 'SIX_ZONE'
    score = 10
    (1..5).each do | n |
      score = score - solution((n.to_f * diameter / 20 + 0.357), sr)
    end
    score = score - (5 * solution((6 * diameter / 20 + 0.357), sr))
  end

  (score.to_f * shots).to_f
end

score_range(h, range) click to toggle source

# File lib/agb_handicap.rb, line 122
def score_range(h, range)
  100 * range * (1.036 ** (h + 12.9)) * 5e-4 * (1 + 1.429e-6 * (1.07 ** (h + 4.3)) * (range * range))
end

solution(operator, score_range) click to toggle source

# File lib/agb_handicap.rb, line 126
def solution(operator, score_range)
  return Math.exp( -(operator / score_range) ** 2 )
end