In my data set I have data from Dec. 1-28th in column header "Date". Because there are 31 days in Dec., I need to estimate the rest of the data for the following dates: 29th, 30th, and 31st. To do so, I want to use a 7 day lookback. By that I mean, the 29th will use data from the 22nd. The 30th will use the data from the 23rd. The 31st will use data from the 24th.