Assign values to dataframe based on index

Question

Having a dataframe as

and another dataframe where i need to put calculated values from the previous df. the val column is a multiplication of values by index

i   j   val
1   1    1
1   2    2
1   3    3
2   1    2
2   2    4
2   3    6
3   1    3
3   2    6
3   3    9

ive tried to calculate it as using a loop but i dont think this approach is the fastest one. How can i accomplish this in a more efficient way?

Do you want the first dataframe to create the combination of i and j? — ResidentSleeper
– ResidentSleeper, Commented Apr 26, 2019 at 16:17
@ResidentSleeper yes the first DF should get the values for the second df — Daniel
– Daniel, Commented Apr 26, 2019 at 16:18

ResidentSleeper · Accepted Answer · 2019-04-26 16:21:25Z

1

IIUC.

df2 = pd.DataFrame(index=pd.MultiIndex.from_product([df.index, df.col])).reset_index()
df2.columns = ['i', 'j']
df2['val'] = df2.i * df2.j

df2
Out[45]: 
   i  j  val
0  1  1    1
1  1  2    2
2  1  3    3
3  2  1    2
4  2  2    4
5  2  3    6
6  3  1    3
7  3  2    6
8  3  3    9

answered Apr 26, 2019 at 16:21

ResidentSleeper

2,4952 gold badges13 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Mark · Accepted Answer · 2019-05-17 08:53:30Z

0

I would suggest:

 df2['i'] = df.index
 df2['j'] = df.col
 df2['val'] = df2['j'] * df2['i']

edited May 17, 2019 at 8:53

answered Apr 26, 2019 at 20:41

Mark

9841 gold badge11 silver badges27 bronze badges

Collectives™ on Stack Overflow

Assign values to dataframe based on index

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related