熊猫。 ValueError：值的长度不匹配索引的长度

Question

请帮助！我有几乎相同的SMA和EMA代码结构。 SMA代码正常，但EMA代码会收到错误：“ValueError：值的长度与索引的长度不匹配。”

SMA（简单移动平均线）代码：

import pandas as pd 
import matplotlib.pyplot as plt 
window_length = 20 
df = pd.read_csv("TWII_2009-2011.csv") 
df=df.set_index('Date') ##### 
close = df['Close'] 
def simple_moving_average(window_length): 
    sma=[] 
    for i in range(len(close)): 
     if i+1 < window_length: 
      sma.append(0) 
     else: 
      sma.append(sum(close[i+1 - window_length : i+1])/window_length) 
    return sma 
df['SMA'] = simple_moving_average(window_length) 

EMA（指数移动平均线）代码：

import pandas as pd 
import matplotlib.pyplot as plt 
window_length = 20 
df = pd.read_csv("TWII_2009-2011.csv") 
df=df.set_index('Date') ##### 
close = df['Close'] 
def exponential_moving_average(window_length): 
    ema = [] 
    j=1 
    for i in range(len(close)): 
     if i+1 < window_length: 
      sma = sum(close[:window_length])/window_length 
      multiplier = 2/float(1 + window_length) 
      ema.append(sma) 
      ema.append(((close[window_length] - sma) * multiplier) + sma) 
     else: 
      tmp = ((i - ema[j]) * multiplier) + ema[j] 
      j = j + 1 
      ema.append(tmp) 
    return ema 
df['EMA'] = exponential_moving_average(window_length) 

Answer 1

您可以附加EMA两次！在第一个'If'语句中而在SMA中只添加一次。删除一个..

for i in range(len(close)): 
      if i+1 < window_length: 
       sma = sum(close[:window_length])/window_length 
       multiplier = 2/float(1 + window_length) 
       ema.append(sma) 
       ema.append(((close[window_length] - sma) * multiplier) + sma) 
      else: 
       tmp = ((i - ema[j]) * multiplier) + ema[j] 
       j = j + 1 
       ema.append(tmp) 
     return ema 

您应该为这些计算查找pandas方法。