It seems the Internet has not answered this question for R yet:
If I have a date. Say the 20th of march: as.Date("2015-03-20")
how do I get, in R, the previous Sunday?
i.e., in the above example, as.Date("2015-03-15").
Here is one approach:
d <- as.Date("2015-03-18") prev.days <- seq(d-6,d,by='day') prev.days[weekdays(prev.days)=='Sunday'] #  "2015-03-15"