gistfile1.rb

  DISPERSION_FACTORS = {50 => 0.5341, 100 => 0.3610, 200 => 0.5145, 500 => 0.9159, 1000 => 0.9088, 5000 => 4.662}

  # Calculate the intake fraction where iF = SUM(popN * DispN) / 1000
  # where popN is the population in an N meter buffer minus the previous population buffer
  def intake_fraction
    fraction = 0
    inner_pop = 0
    DISPERSION_FACTORS.each do |buffer, value|
      pop_in_buffer = send("pop#{buffer}m").to_i
      fraction += (pop_in_buffer - inner_pop) * value * 0.62 * 14.5
      inner_pop = pop_in_buffer
    end
    return fraction / 1000
  end