数据分析(八)标准差
样本:S = [s1, s2, ..., sn] 平均值:m = (s1+s2+...+sn)/n 离差:D = [d1, d2, ..., dn], di = si-m 离差方:Q = [q1, q2, ..., qn], qi = di**2 总体方差:v = (q1+q2+...+qn)/n 总体标准差:s = sqrt(v),方均根 样本方差:v' = (q1+q2+...+qn)/(n-1) 样本标准差:s' = sqrt(v'),方均根 np.std(array) # 总体标准差 np.std(array, ddof=1) # 样本标准差 # 中位数 import numpy as np import datetime as dt 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, volumes = \ np.loadtxt(