2024-election-modelling/main.go

package main

import (
	"encoding/csv"
	"fmt"
	rand "math/rand/v2"
	"os"
	"strconv"
	// "strings"
)

/* Structs */
type State struct {
	Name                       string
	Votes                      int
	VictoriousPartyPerElection map[string]string
}

type VotesForEachParty struct {
	Democrats   int
	Republicans int
}

// type src = *rand.Rand

/* Globals */
var r = rand.New(rand.NewPCG(uint64(100), uint64(2224)))

/* Load data from csvs */
func readStates() ([]State, error) {
	var states map[string]State = make(map[string]State)

	/* Electoral college votes for the 2024 election*/
	votes_file, err := os.Open("data/electoral-college-votes.csv")
	// votes_file, err := os.Open("data/electoral-college-votes-2010-census.csv")
	if err != nil {
		return nil, fmt.Errorf("error opening the votes file: %v", err)
	}
	defer votes_file.Close()

	votes_reader := csv.NewReader(votes_file)
	if _, err := votes_reader.Read(); err != nil { // Skip header
		return nil, fmt.Errorf("error reading votes header: %v", err)
	}
	for {
		csv_record, err := votes_reader.Read()
		if err != nil {
			break // EOF or an error
		}
		votes, err := strconv.Atoi(csv_record[1])
		if err != nil {
			continue // Error in converting votes, skip this record
		}
		state := csv_record[0]
		if _, exists := states[state]; !exists {
			states[state] = State{Name: state, Votes: votes, VictoriousPartyPerElection: make(map[string]string)}
		}
	}

	/* Election results */
	var years = []string{"2000", "2004", "2008", "2012", "2016", "2020"}
	for _, year := range years {
		results_filename := fmt.Sprintf("data/results/%s.csv", year)
		results_file, err := os.Open(results_filename)
		if err != nil {
			return nil, fmt.Errorf("error opening the results file for %s: %v", year, err)
		}
		resultsReader := csv.NewReader(results_file)
		if _, err := resultsReader.Read(); err != nil { // Skip header
			return nil, fmt.Errorf("error reading results header for %s: %v", year, err)
		}
		for {
			record, err := resultsReader.Read()
			if err != nil {
				break // EOF or an error
			}
			state, party := record[0], record[1]
			data, exists := states[state]
			if !exists {
				continue // State not found in votes map, skip
			}
			// Update the party winning in the specific year
			data.VictoriousPartyPerElection[year] = party
			states[state] = data
		}

		results_file.Close()
	}

	// Convert statesData map to a slice for returning
	var states_slice []State
	for _, state := range states {
		states_slice = append(states_slice, state)
	}

	return states_slice, nil
}

func sampleFromState(state State) VotesForEachParty {
	switch state.Name {
	case "Nebraska":
		// 2000: R
		// 2004: R
		// 2008: Split, 1 D, 4 R
		// 2012: R
		// 2016: R
		// 2020: Split, 1 D, 4 R
		p_split := 2.0 / 6.0
		if r.Float64() < p_split {
			return VotesForEachParty{Democrats: 1, Republicans: 4}
		} else {
			return VotesForEachParty{Democrats: 0, Republicans: 5}
		}
	case "Maine":
		// 2000: D
		// 2004: D
		// 2008: D
		// 2012: D
		// 2016: Split: 3 D, 1 R
		// 2020: Split, 3 D, 1 R
		p_split := 2.0 / 6.0
		if r.Float64() < p_split {
			return VotesForEachParty{Democrats: 3, Republicans: 1}
		} else {
			return VotesForEachParty{Democrats: 1, Republicans: 0}
		}
	default:
		{
			p_republican := 0.0
			for _, party := range state.VictoriousPartyPerElection {
				if party == "R" {
					p_republican++
				}
			}
			p_republican = p_republican / float64(len(state.VictoriousPartyPerElection))
			if r.Float64() < p_republican {
				return VotesForEachParty{Democrats: 0, Republicans: state.Votes}
			} else {
				return VotesForEachParty{Democrats: state.Votes, Republicans: 0}
			}
		}
	}
}

func simulateElection(states []State) int {

	republican_seats := 0
	for _, state := range states {
		election_sample := sampleFromState(state)
		republican_seats += election_sample.Republicans
		/*
			fmt.Printf("%s: Votes: %d,\n\tWinners: ", state.Name, state.Votes)
			for year, party := range state.VictoriousPartyPerElection {
				fmt.Printf("[%s: %s] ", year, party)
			}

			fmt.Printf("\n\tSample: Democrat seats: %d, Republican seats: %d", election_sample.Democrats, election_sample.Republicans)
			fmt.Println()
		*/
	}

	// fmt.Printf("\nDemocrat seats: %d\n", republican_seats)
	fmt.Printf(" (%d) ", republican_seats)
	if republican_seats >= 270 {
		return 1
	} else {
		return 0
	}

}

func main() {
	states, err := readStates()
	if err != nil {
		fmt.Println("Error:", err)
		return
	}

	n_sims := 100_000

	p_republicans := 0.0
	for i := 0; i < n_sims; i++ {
		result := simulateElection(states)
		fmt.Printf("Election result: %d\n", result)
		if result == 1 {
			p_republicans++
		}
	}
	p_republicans = p_republicans / float64(n_sims)
	fmt.Printf("%% republicans: %f\n", p_republicans)

}