Dataframe
df=pd.DataFrame({"sym":["a","a","aa","aa","aa","a","ab","ab","ab"],
"id_h":[2.1, 2.2 , 2.5 , 3.1 , 2.5, 3.8 , 2.5, 5,6],
"pm_h":[np.nan, 2.3, np.nan , 2.8, 2.7, 3.7, 2.4, 4.9,np.nan]})
want to fill pm_h nan values with max id_h value of each "sys" group i.e. (a, aa, ab)
Required output:
df1=pd.DataFrame({"sym":["a","a","aa","aa","aa","a","ab","ab","ab"],
"id_h":[2.1, 2.2 , 2.5 , 3.1 , 2.5, 3.8 , 2.5, 5,6],
"pm_h":[3.8, 2.3, 3.1 , 2.8, 2.7, 3.7, 2.4, 4.9, 6})
question from:
https://stackoverflow.com/questions/65885577/fillna-with-max-value-of-each-group-in-python