我想添加新列并根据条件填充值。
df:
indicator, value, a, b
1, 20, 5, 3
0, 30, 6, 8
0, 70, 2, 2
1, 10, 3, 7
我想基于指标添加一个新列(value_new
)。如果为indicator == 1
,则为value_new = a*b
,否则为value_new = value
。
df:
indicator, value, a, b, value_new
1, 20, 5, 3, 15
0, 30, 6, 8, 30
0, 70, 2, 2, 70
1, 10, 3, 7, 21
我尝试了以下操作:
value_new = []
for in in range(1, len(df)):
if indicator[i] == 1:
value_new.append(df['a'][i]*df['b'][i])
else:
value_new.append(df['value'][i])
df['value_new'] = value_new
Error: 'Length of values does not match length of index'
而且我也尝试过:
for in in range(1, len(df)):
if indicator[i] == 1:
df['value_new'][i] = df['a'][i]*df['b'][i]
else:
df['value_new'][i] = df['value'][i]
KeyError: 'value_new'
您可以使用np.where
:
np.where
打印:
df['value_new'] = np.where(df['indicator'], df['a']*df['b'], df['value'])
print(df)