Sample R script for finding winners in a proportional election system

ProportionalElectionResults.R

# Sample R script for finding winners in a proportional election system
# by Sharon Machlis

# This example assumes a spreadsheet with a list of candidates with column headers
# Municipality, Party, Place, Name, Variable
# and a spreadsheet with a list of results with column headers
# Municipality, Red, Blue, Green (Red, Blue, Green being sample political party names)

# See sample spreadsheet format at
# https://onedrive.live.com/redir?resid=7DDBA42BF10D288B!662&authkey=!AAFnW1H3wGiZgQU&ithint=file%2c.xlsx

# Read in data from spreadsheets: candidates list and election results
library("xlsx")
candidates <- read.xlsx("test.xlsx", sheetName = "candidates", stringsAsFactors=FALSE)
results <- read.xlsx("test.xlsx", sheetName = "results", stringsAsFactors=FALSE)


########## USING data.tables ###############
library(data.table)

# Create data tables dtcandidates and dtresults from the data frames we just made above
dtcandidates <- data.table(candidates)
dtresults <- data.table(results)

# setkey tells data.table which column variables we want to search or group by
setkey(dtcandidates, Municipality, Party, Place)
setkey(dtresults, Municipality)

# This function takes a municipality name and returns which candidates won seats
getwinners <- function(muni){
  numwinners <- dtresults[muni] # Gets the municipality's row from the results spreadsheet
  numwinners$Municipality <- NULL # Deletes the Municipality column since we don't need that
  
  # Find all the parties that had at least 1 winner
  winningparties <- apply(numwinners, 2, function(x) x > 0) 
  parties <- subset(numwinners, select=winningparties)
  
  # Get a vector of names of winning parties (just column names from parties)
  partynames <- names(parties)
  
  # Create an empty data frame to store info about each winning candidate
  myresults <<- data.frame(Municipality=character(0), Party=character(0), Place=integer(0), Name=character(0), Variable=character(0))
  
  # This loop goes through each party that won seats and finds winning candidates for each party
  

  for(p in partynames){  
    # Extract number of seats won by the party:
    themax <- as.numeric(subset(parties, select=p)) 
    
    # Find all the candidates from that party with a place less than or equal to number of winners
    elected <- dtcandidates[J(muni, p, 1:themax)]    
    
    # Add those rows to the originally empty data frame we created above
    myresults <<- rbind(myresults, elected)
  }
  
  return(myresults)
  
}

# Here, store all the municipalities you have results for in the dtresults data.table
cities <- dtresults$Municipality

# Run the getwinners function on each one of the cities
myresults_list <- lapply(cities, getwinners)

# Turn the list of results in myresults_list into a single data.table:
myresultsdt <- do.call(rbind, myresults_list)