Ema cross over stretgy

# Ema cross over strategy
def ema_crossover(data, short_window = 12, long_window = 26):
  signals = pd.DataFrame(index = data.index)
  signals['signal'] = 0.0
  
  signals['short_mva'] = data['Close'].rolling(window = short_window, min_periods = 1, center = False).mean()
  signals['long_mva'] = data['Close'].rolling(window = long_window, min_periods = 1, center = False).mean()
  
  signals['signal'][short_window:] = np.where(signals['short_mva'][short_window:] > signals['long_mva'][short_window:], 1.0, 0.0)
  
  signals['positions'] = signals['signal'].diff()
  
  return signals