pandas求五日線並畫圖

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt 

stock_data = pd.read_csv('000078.csv',encoding='gbk')
stock_data = stock_data[['日期','股票代碼','收盤價','成交量']]

stock_data.sort_values('日期',inplace=True)
stock_data['五日均線'] = stock_data['收盤價'].rolling(window=5).mean() 

x = (stock_data.ix[30:]['五日均線']).idxmax()
plt.plot(np.arange(x+1),stock_data.ix[30:]['五日均線'])
plt.show()