dataMaid check function: deal with "key" variables that do not uniquely identify rows

dataMaid_isIDvar.R

#'dataMaid_isIDvar.R
#'
#'This function identifies "Key" and similar variables and stops dataMaid::makeDataReport from creating
#'visualizations and/or other inappropriate summaries.  Instead it outputs a table with minimal information 
#'(see https://cran.rstudio.com/web/packages/dataMaid/vignettes/extending_dataMaid.html for inspiration).
#'
#' @example
#' makeDataReport(toyData, output = "html", 
#'                preChecks = c("isKey", "isSingular", "isSupported", "isIDvar"))

isIDvar <- function(v, nMax = NULL, ...) {
  out <- list(problem = FALSE, message = "")
  
  if (class(v) %in% c("character", "factor")) {
    #Check if there are more than 49 unique values
    nVals <- length(unique(v[!is.na(v)]))
    
    if (nVals > 49) {
      out$problem <- TRUE
      out$message <- paste("This variable is an ID, Name, or other string-formatted variable with too many unique values to list.\n\n",
                           "-------------------------------------------------------\n",
                           "Feature                                          Result\n",
                           "---------------------------- --------------------------\n",
                           "Variable Type:                    ", class(v), "\n\n",
                           "Number of missing obs.:           ", sum(is.na(v)), "(", round(sum(is.na(v))/length(v)*100,2),"%)\n\n",
                           "Number of unique values:          ", nVals, "\n\n",
                           "-------------------------------------------------------\n")
    }
  }
  return(out)
}

isIDvar <- checkFunction(isIDvar, 
                         description = "Check for likely ID vars that don't uniquely ID the rows.",
                         classes = c("character", "factor"))