R/fill_down.R

In svenhalvorson/SvenSFPS: Sven's R Jiggering

# Alright so I often encounter a scenarios where I want to fill
# in values of a column with the last non-NA value above it
# so it should turn c(1,NA,NA,3,NA,2,NA to c(1,1,1,3,3,2,2)
# Often this happens with people's excel sheets having split cells
# string parameter denotes whether we want to treat "" like NA



fill_down <- function(x, string = FALSE){

  if(!is.atomic(x)){
    stop("x must be atomic")
  }

  # Can define this function to determine if strings should be used
  if(string){
    check_mia <- function(i){
      is.na(x[i])
    }
  }else{
    check_mia <- function(i){
      is.na(x[i]) | x[i] == ''
    }
  }



  # Store the most recent non NA value and loop through the vector
  temp = NA
  for(i in 1:length(x)){

    # First case is the first entry is NA, just keep going
    if(is.na(temp) & check_mia(i)){
      next()
    }

    # If we hit a real value, save it
    if(!is.na(x[i])){
      temp = x[i]
      next()
    }

    # Finally, if we have a value stored and x[i] is NA
    if(!is.na(temp) & check_mia(i)){
      x[i] = temp
    }
  }


  return(x)
}