熊猫。 ValueError：值的长度与索引的长度不匹配

Question

请帮忙！我的 SMA 和 EMA 代码结构几乎相同。 SMA 代码正常，但 EMA 代码出错：“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

你附加了两次 ema！在第一个“If”语句中，而在 SMA 中，您只附加一次。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

您应该查找用于这些计算的 pandas 方法。