R data.table set new column with logical value if a weekday is between a date range

Question

I have a data.table object with two date columns, from and to. I want to create a new column to determine if a specific w

Answer 1

Here's my example:

library(parallel)

process <- function(){


  from <- seq(as.Date("1950-01-01"), by = "day", length = 100000)
  to <- seq(as.Date("1950-01-04"), by = "day", length = 100000)

  DT <- data.frame(from,to)

  Ncores <- detectCores()

  flagList <- mclapply(1:nrow(DT),function(id){

    4 %in% strftime(seq(as.Date(DT[id,1]), as.Date(DT[id,2]), by="day"), format="%w")

  },mc.cores=Ncores)

  flag <- unlist(flagList)

  return(cbind(DT,flag))

}

It takes just 15 sec for 100k rows on my i7 processor. Hope this helps.