Find most recent Monday for a dataframe

Question

I have a dataframe object, and among the fields in it, I have a dates:

df$dates

I need to add a column which is \'Week Starting\', i.e.

Answer 1

If you want nearest any day and hour to the current date, use this function:

dayhour <- function(day,hour){
   k <- as.Date(Sys.time())+day-as.numeric(format(strptime(Sys.time(),format="%Y-%m-%d %H:%M:%S"), format ='%u'))
   dh <- format(strptime(paste(k,hour), format="%Y-%m-%d %H"), format="%A %H")
   return(dh)
}

For the weekdays use 0 to 6 as day argument for sunday to saturday respectively:

> dayhour(0,17)
[1] "Sunday 17"