class FinTools

# File lib/fintools.rb, line 43
def calcMACD(price_arr, ema_long, ema_short, ema_diff)
  closing_prices = price_arr.map { | r |
    r[:cls]
  }
  ema26 = calc_ema(closing_prices, ema_long)
  ema12 = calc_ema(closing_prices, ema_short)
  
  return calc_ema(closing_prices, ema_diff)
end

# File lib/fintools.rb, line 37
def calc_ema(arr, period)
  my_data = Indicators::Data.new(arr)
  return my_data.calc(:type => :ema, :params => period).output
end

# File lib/fintools.rb, line 26
def histvola(values)
  stddev = standard_deviation(values)
  return stddev * Math.sqrt(254)
end

# File lib/fintools.rb, line 10
def mean(arr)
  arr.sum / arr.length.to_f
end

# File lib/fintools.rb, line 14
def sample_variance(arr)
  m = mean(arr)
  sum = arr.inject(0) { | accum, i | 
    accum + (i - m) ** 2
  }
  sum / (arr.length - 1).to_f
end

# File lib/fintools.rb, line 32
def sharpe_ratio(rets)
  return mean(rets) / standard_deviation(rets)
end

# File lib/fintools.rb, line 22
def standard_deviation(arr)
  return Math.sqrt(sample_variance(arr))
end

# File lib/fintools.rb, line 5
def sum(arr)
  arr.inject(0) { | accum, i | accum + i
}
end