Pandas：用列最大值替换列中的所有值

Question

I have the following dataframe

            NDQ        CFRI        NFFV        [more columns....]
2002-01-24 92.11310000 57.78140000 90.95720000
2002-01-25 57.97080000 91.05430000 58.19820000

I want to set all values in a column equal to the maximum value of the respective column.

Desired output:

            NDQ        CFRI        NFFV        [more columns....]
2002-01-24 92.11310000 91.05430000 90.95720000
2002-01-25 92.11310000 91.05430000 90.95720000

I have attempted to map it out to the result of df.max() , but struggled with the implementation and also feel like there would be an easier solution available.

Any help would be greatly appreciated.

Answer 1

You can use df.clip and set the lower param to df.max :

From Docs:

lower : float or array_like, default None Minimum threshold value. All values below this threshold will be set to it.

df.clip(df.max(),axis=1)

---

                NDQ     CFRI     NFFV
2002-01-24  92.1131  91.0543  90.9572
2002-01-25  92.1131  91.0543  90.9572

Answer 2

To set all values in a column equal to the maximum value of the respective column I would suggest to follow below code.

df['NDQ']=df.NDQ.max()

or

df['NDQ_Max']=df.NDQ.max()

df.clip is used to Assigns values outside boundary to boundary values. But as you want to set all the values in a particular values you may not need to use that. Please see the link

https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.clip.html