Write a function named count that takes one argument, a character string indicating the cause of death. The function should then return an integer representing the number of homicides from that cause in the dataset. If no cause of death is specied, then the function should return an error message via the stop function.

count.R

# count.R

# setwd("~/ComputingForDataAnalysis/Assignment4")

count <- function(cause = NULL) {
  ## Check that "cause" is non-NULL; else throw error
  if (is.null(cause)) {
    stop("Cause has not been specified.")
  }
  
  ## Check that specific "cause" is allowed; else throw error
  allowed_causes = c("asphyxiation", "blunt force", "other", "shooting", "stabbing", "unknown")
  
  if (!cause %in% allowed_causes) {
    stop("The cause specified is not allowed.")
  }
  
  ## Read "homicides.txt" data file
  homicides <- readLines("homicides.txt")
  
  ## Extract causes of death
  cause_regex_pattern <- "[Cc]ause"
  # 212, 213, 236, 238, 515 records do not have cause of death.
  # To see this, use the following statement
  # grep(pattern=cause_regex_pattern, x=homicides)
  matched_positions <- regexpr(pattern=cause_regex_pattern, text=homicides)
  my_count = 0
  if (cause == "asphyxiation") {
    my_count = length(grep("Cause: [Aa]sphyxiation", homicides))
  }
  else if (cause == "blunt force") {
    my_count = length(grep("Cause: [Bb]lunt [Ff]orce", homicides))
  }
  else if (cause == "other") {
    my_count = length(grep("Cause: [Oo]ther", homicides))
  }
  else if (cause == "shooting") {
    my_count = length(grep("Cause: [Ss]hooting", homicides))
  }
  else if (cause == "stabbing") {
    my_count = length(grep("Cause: [Ss]tabbing", homicides))
  }
  else if (cause == "unknown") {
    my_count = length(grep("Cause: [Uu]nknown", homicides))
  }
  else {stop("Impossible error.")}
  
  ## Return integer containing count of homicides for that cause
  return(my_count)
}