Pandas merging rows with the same value and same index

Question

I have a DataFrame with an index called SubjectID and a column Visit. Subjects have multiple Visits and either an integer value or an N/A for

Answer 1

You can use groupby.first or groupby.last to get the first/last non-null value for each column within the group. For the example data, the output would be the same for either method:

df = df.groupby(['SubjectID', 'Visit']).first().reset_index()

The resulting output:

  SubjectID  Visit  Value1  Value2
0        B1      1    1.57    1.75
1        B1      2     NaN    1.56