If today's date is Saturday, Sunday, or Monday then set today's date to last Friday, else-CodePudding

With only the System Libraries (preferably), how do I set today's date to last Friday if today falls on Saturday, Sunday, or Monday, else set to today's date?

todaysDate <- Sys.Date()

if(weekdays(todaysDate) == "Saturday" || weekdays(todaysDate) == "Sunday" 
   || weekdays(todaysDate) == "Monday") {
  todaysDate == ???} else {
    todaysDate <- Sys.Date()
  }

Thanks in advance.

Systems used:

R version: 4.1.1 (2021-08-10)
RStudio version: 1.4.1717
OS: macOS Catalina version 10.15.7 and macOS Big Sur version 11.6

CodePudding user response：

You could use the logic:

todaysDate <- Sys.Date()
today <- weekdays(todaysDate)

if(today == "Saturday")
  todaysDate <- todaysDate - 1
else if (today == "Sunday") 
   todaysDate <- todaysDate - 2
else if (today == "Monday") 
   todaysDate <- todaysDate - 3

CodePudding user response：

We may do this with match on sequence of dates before the 'todaysDate' that matches the 'Friday'

if(weekdays(todaysDate) %in% c("Saturday", "Sunday", "Monday")) {
      s1 <- todaysDate - (1:8)
      todaysDate <- s1[match('Friday', weekdays(s1))]
    }

CodePudding user response：

An other solution might be a recursive function:

dayFun <- function(x) {
  if (weekdays(x) %in% c("Sunday", "Saterday", "Monday")) {
    return(dayFun(x-1))
  } else {
    return(x)
  }
}
dayFun(Sys.Date())

note that the result of weekdays depends on the language setting of the machine so if that is a concern some more thoughts are needed