从新生成的列值返回动态值

Question

我有2列，我想要diff列作为输出。我尝试使用循环迭代。如果我传递值数组，我想要diff列数组。

 l                h              diff           
 100.87           100.87         max(h-l)

99.800778         100.87         max ((h-l),diff[0])

101.1281283     101.1281283      max ((h-l),diff[1])     

106.4575807     106.4575807      max ((h-l),diff[2])

109.3212896     109.3212896        .....

107.7907916     109.3212896

105.128359      109.3212896

103.8668187     109.3212896

108.9978396     109.3212896

110.0006197     110.0006197

有人可以帮助我。

Answer 1

IIUC，您需要cummax：

df['diff'] = df['h'] - df['l']
df['diff'] = df['diff'].cummax()

您可以在一行中执行此操作：

df['diff'] = (df['h'] - df['l']).cummax()

输出：

            l           h      diff
0  100.870000  100.870000  0.000000
1   99.800778  100.870000  1.069222
2  101.128128  101.128128  1.069222
3  106.457581  106.457581  1.069222
4  109.321290  109.321290  1.069222
5  107.790792  109.321290  1.530498
6  105.128359  109.321290  4.192931
7  103.866819  109.321290  5.454471
8  108.997840  109.321290  5.454471
9  110.000620  110.000620  5.454471