求基金的累计收益率，急！！

想要求出样本期与基期之间的差，但最后表现出来的形式是NaN，这个怎么解决？

我猜想你是想要这种效果。

import pandas as pd
from random import randint
import numpy as np
lst = [ [randint(1,100) for n in range(4) ] for m in range(11)]
print(lst)

df1 = pd.DataFrame(lst,columns=['H1','H2','H3','H4'])
print(df1)
a = np.array(df1.loc[10:10])
print(a)
for i in range(1,10):
    b = np.array(df1.loc[i:i])
    c = b - a
    print(pd.DataFrame(c,columns=['H1','H2','H3','H4']))