R/halstead.R

In JSzitas/qa:

#' Calculate halstead software complexity measures
#'
#' @description Calculate the halstead software complexity measures for a given file
#' @param file The file to calculate for - a file-path.
#'
#' @return A list with following elements:
#' \itemize{
#' \item{program vocabulary}
#' \item{program length}
#' \item{program length (estimated)}
#' \item{program volume}
#' \item{program difficulty}
#' \item{program effort}
#' \item{time to program (minutes)}
#' \item{number of bugs}
#' }
#' @details See also \url{ https://en.wikipedia.org/wiki/Halstead_complexity_measures }
#' @export
halstead_measures <- function(file)
{
  tokens <- sourcetools::tokenize_file(file)

  tokens <- tokens[ !(tokens$type %in% c("whitespace","comment")),]
  tokens[ tokens$type %in% c("keyword","bracket","comma"), "type" ] <- "operator"
  tokens[ tokens$type %in% c("symbol","number","string"), "type" ] <- "operand"

  operators <- tokens[ tokens$type == "operator", "value"]
  operands <- tokens[ tokens$type == "operand", "value"]

  eta_1 <- length( unique( operators ))
  eta_2<- length( unique( operands ))

  N_1 <- length(operators)
  N_2 <- length(operands)

  result <- list()
  result[["program_vocabulary"]] <- eta_1 + eta_2
  result[["program_length"]] <- N_1 + N_2
  result[["program_length_estimate"]] <- (eta_1 * log2(eta_1)) + (eta_2 * log2(eta_2))
  result[["program_volume"]] <- result[["program_length"]] * log2(result[["program_vocabulary"]])
  result[["program_difficulty"]] <- (eta_1/2) * (N_2/eta_2)
  result[["program_effort"]] <- result[["program_difficulty"]] * result[["program_volume"]]
  result[["time_to_program_minutes"]] <- round( result[["program_effort"]]/18/60, 2)
  result[["number_of_bugs"]] <- result[["program_volume"]]/3000

  return(result)
}