weather_hash.rb

require('csv')

class AnnualWeather
  def initialize (file_name)
    @readings = []

    CSV.foreach(file_name, headers: true) do |row|
      @readings << {
        :date => Date.parse(row[2]),
        :high => row[10].to_f,
        :low  => row[11].to_f,
      }
    end
  end
  
  def mean
    return 0.0 if @readings.size.zero?
    
    total = @readings.reduce(0.0) do |sum, reading|
      sum + (reading[:high] + reading[:low]) / 2.0
    end
    
    total / @readings.size.to_f
  end
end