算数平均值:
m = (s1 + s2 + ... + sn) / n
算数平均值表示对真值的无偏估计。
np.mean(array)
array.mean()
案例:计算收盘价的算术平均值。
#算数 import numpy as np import matplotlib.pyplot as mp import datetime as dt import matplotlib.dates as md def dmy2ymd(dmy): """ 把日月年转年月日 :param day: :return: """ dmy = str(dmy, encoding='utf-8') t = dt.datetime.strptime(dmy, '%d-%m-%Y') s = t.date().strftime('%Y-%m-%d') return s dates, opening_prices, \ highest_prices, lowest_prices, \ closing_prices = \ np.loadtxt('aapl.csv', delimiter=',', usecols=(1, 3, 4, 5, 6), unpack=True, dtype='M8[D],f8,f8,f8,f8', converters={1: dmy2ymd}) # 日月年转年月日 print(dates) # 绘制收盘价的折现图 mp.figure('APPL', facecolor='lightgray') mp.title('APPL', fontsize=18) mp.xlabel('Date', fontsize=14) mp.ylabel('Price', fontsize=14) mp.grid(linestyle=":") # 设置刻度定位器 # 每周一一个主刻度,一天一个次刻度 ax = mp.gca() ma_loc = md.WeekdayLocator(byweekday=md.MO) ax.xaxis.set_major_locator(ma_loc) ax.xaxis.set_major_formatter(md.DateFormatter('%Y-%m-%d')) ax.xaxis.set_minor_locator(md.DayLocator()) # 修改dates的dtype为md.datetime.datetiem dates = dates.astype(md.datetime.datetime) mp.plot(dates, closing_prices, color='dodgerblue', linewidth=2, linestyle='--', alpha=0.8, label='APPL Closing Price') #计算收盘价的均值 mean = np.mean(closing_prices) mean = closing_prices.mean() mp.hlines(mean,dates[0],dates[-1],colors='orangered', label='mean') mp.gcf().autofmt_xdate() mp.show()