Python pandas - dividing column by another column

Question

I am trying to add a column to my DataFrame , which is the product of separating two other columns, for example:

 df['$/hour'] = df['$']/df['hours'] 

This works fine, but if the value in ['hours'] less than 1 , then the value of ['$/hour'] larger than the value in ['$'] , which is not what I want.

Is there a way to control the operation, so if ['hours'] < 1 , then df['$/hour'] = df['$'] ?

Answer 1

You can use 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 

Answer 2

You can also filter and select indexes to set using DataFrame.loc :

 df['$/hour'].loc[df['hours']>=1] = df['$']/df['hours'] df['$/hour'].loc[df['hours']<1] = df['$'] 

Answer 3

 df['$/hour'] = df.apply(lambda x: x['$'] if x['$'] < 1 else x['$']/x['hours'], axis=1)