python pandas - 将列除以另一列
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python pandas - dividing column by another column
提问by Charon
I'm trying to add a column to my DataFramewhich is the product of division of two other columns, like so:
我正在尝试向我的列添加一列，DataFrame它是其他两列除法的乘积，如下所示：
df['$/hour'] = df['$']/df['hours']
This works fine, but if the value in ['hours']is less than 1, then the ['$/hour']value is greater than the value in ['$'], which is not what I want.
这工作正常，但是如果 in 的值['hours']小于1，则该['$/hour']值大于 中的值['$']，这不是我想要的。
Is there a way of controlling the operation so that if ['hours'] < 1then df['$/hour'] = df['$']?
有没有办法控制操作，如果['hours'] < 1那么df['$/hour'] = df['$']？
采纳答案by jezrael
You can use numpy.where:
您可以使用numpy.where：
print df
hours $
0 0 8
1 0 9
2 0 9
3 3 6
4 6 4
5 3 7
6 5 5
7 10 1
8 9 3
9 3 6
10 5 4
11 5 7
df['$/hour'] = np.where(df['hours'] < 1, df['hours'], df['$']/df['hours'])
print df
hours $ $/hour
0 0 8 0.000000
1 0 9 0.000000
2 0 9 0.000000
3 3 6 2.000000
4 6 4 0.666667
5 3 7 2.333333
6 5 5 1.000000
7 10 1 0.100000
8 9 3 0.333333
9 3 6 2.000000
10 5 4 0.800000
11 5 7 1.400000
回答by Brian Huey
df['$/hour'] = df.apply(lambda x: x['$'] if x['$'] < 1 else x['$']/x['hours'], axis=1)
回答by agold
You can also filter and select the indexes to set with DataFrame.loc:
您还可以过滤和选择要设置的索引DataFrame.loc：
df['$/hour'].loc[df['hours']>=1] = df['$']/df['hours']
df['$/hour'].loc[df['hours']<1] = df['$']
