How to multiply numeric elements of a dataframe by a scalar?

Asked Aug 12 '20 at 22:29

Active Aug 12 '20 at 22:29

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I have a simple dataframe, and I would like each numeric element multiplied by a scalar. However, some columns of my dataframe are strings. These strings should be included as-is in the final dataset. The real dataset is roughly 150 columns wide, with some unknown datatypes. So my solution would have to be able to scale up.

Input: 
A    B    C    D    E    F    G
DS   DZ   3    2    1    3    5
CA   3S   4    1    4    1    4 
DG   dD   2    2    5    7.1  2
DDS  $Z   1.1  2    3    4    5

multiply numbers by 3

Output:
A    B    C    D    E    F    G
DS   DZ   9    6    3    9    15
CA   3S   12   3    12   3    12 
DG   dD   6    6    15   21.3 6
DDS  $Z   3.3  6    9    12   15

asked Aug 12 '20 at 22:29

Dylan Moore

1

did you try `df * 3`? – Paul H Aug 12 '20 at 22:31
@Paul, that would repeat the string entries as well – sammywemmy Aug 12 '20 at 22:33
throw them into the index – Paul H Aug 12 '20 at 22:33
1

Try : ``df.loc[:, df.dtypes != "object"] = df.select_dtypes("number") * 3`` – sammywemmy Aug 12 '20 at 22:37
Use `mask = df.select_dtypes(include=np.number).columns; df.loc[:, mask] = df.loc[:, mask]*3` – Space Impact Aug 12 '20 at 22:38
@sammywemmy this solution worked for me, thank you! – Dylan Moore Aug 12 '20 at 23:01

How to multiply numeric elements of a dataframe by a scalar?

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