How to use custom function to create new binary variables within existing dataframe?

Question

I\'m trying to create a custom function that generates new binary variables in an existing dataframe. The idea is to be able to feed the function with the diagnosis description

Answer 1

If you are intending to only work with one diagnosis at a time, this will work. I took the liberty of renaming arguments to be a little easier to work with in the code.

diagnosis_func <- function(data, target_col, icd, new_col){
  pattern <- sprintf("^(%s)", 
                     paste0(icd, collapse = "|"))

  data[[new_col]] <- grepl(pattern = pattern, 
                           x = data[[target_col]]) + 0L
  data
}

diagnosis_func(patient_db, "diag_1", "2851", "Anemia")

# Multiple codes for a single diagnosis
diagnosis_func(patient_db, "diag_1", c("8661", "8651"), "Dx")

If you want to spruce it up a little to prevent inadvertent mistakes, you can install the checkmate package and use this version. This will

diagnosis_func <- function(data, target_col, icd, new_col){

  coll <- checkmate::makeAssertCollection()

  checkmate::assert_class(x = data,
                          classes = "data.frame",
                          add = coll)

  checkmate::assert_character(x = target_col,
                              len = 1,
                              add = coll)

  checkmate::assert_character(x = icd,
                              add = coll)

  checkmate::assert_character(x = new_col,
                              len = 1,
                              add = coll)

  checkmate::reportAssertions(coll)

  pattern <- sprintf("^(%s)", 
                     paste0(icd, collapse = "|"))

  data[[new_col]] <- grepl(pattern = pattern, 
                           x = data[[target_col]]) + 0L
  data
}

diagnosis_func(patient_db, "diag_1", "2851", "Anemia")