combine two data frames and aggregate
问题 I am having 2 data frames in the below format: dt1 id col1 col2 col3 col4 ___ ____ ____ _____ _____ 1 2 3 1 2 2 3 4 1 1 3 1 1 1 1 4 1 2 1 2 5 1 1 1 1 6 1 2 1 2 dt2 id col1 col2 col3 col4 ___ ____ ____ _____ _____ 1 1 3 1 2 2 3 4 1 0 4 1 1 1 1 6 1 2 1 2 9 2 1 1 1 12 1 2 1 2 and I want to aggregate and combine these two data frames by the id and the resulting dataframe like dt3 id col1 col2 col3 col4 ___ ____ ____ _____ _____ 1 3 6 2 4 2 6 8 2 1 3 1 1 1 1 4 2 3 2 3 5 1 1 1 1 6 2 4 2 4 9 2 1 1 1