How can I keep track of total transaction amount sent from an account each last 6 month?
问题 This is my transaction data data id from to date amount <int> <fctr> <fctr> <date> <dbl> 19521 6644 6934 2005-01-01 700.0 19524 6753 8456 2005-01-01 600.0 19523 9242 9333 2005-01-01 1000.0 … … … … … 1055597 9866 9736 2010-12-31 278.9 1053519 9868 8644 2010-12-31 242.8 1052790 9869 8399 2010-12-31 372.2 Now for each distinct account in from column, I want to keep track of how much transaction amount they sent over last 6 month at the time the transaction was made and so I want to do it