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JavaScript What is wrong with my method for predicting the election?

  1. Jul 13, 2016 #1
    Given the fact that there are 51 states and districts, there are 251 subcollections of the 51 states, which I can't possibly iterate over entirely. So what I do is find 210 subcollections of states whose electoral votes summed are 270 or greater. I then sum together the probabilities of Trump winning each of those 210 collection of states. Finally, I multiply that sum by 241.

    Anything wrong with that? Because I'm getting a results that seems wrong.
     
  2. jcsd
  3. Jul 13, 2016 #2

    QuantumQuest

    User Avatar
    Gold Member

    You're extrapolating a small sample - comparing to (##2^{51}##), by a huge number (##2^{41}##) so the result is way off.
     
  4. Jul 17, 2016 #3
    Can you help me figure out why this is always calculating to ~0.99??? It should be calculating to ~0.50 since I put an equal chance of an R or D winning.

    Code (Text):

    const VOTES_TO_WIN = 270;

    // State name, number of electoral votes, and Republican and
    // Democrat nominee polling percent average taken from
    // RealClearPolitics.com, rounded to nearest integer
    const dataByState = {
        'Washington' : { ElectoralVotes : 12, RChance: 50, DChance: 50 },
        'Oregon': { ElectoralVotes: 7, RChance: 50, DChance: 50 },
        'California': { ElectoralVotes: 55, RChance: 50, DChance: 50 },
        'Idaho' : { ElectoralVotes: 4, RChance : 50, DChance: 50 },
        'Nevada' : { ElectoralVotes: 6, RChance : 50, DChance: 50 },
        'Montana' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'Wyoming' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'Colorado' : { ElectoralVotes: 9, RChance : 50, DChance: 50 },
        'New Mexico' : { ElectoralVotes: 5, RChance : 50, DChance: 50 },
        'Utah' : { ElectoralVotes: 6, RChance : 50, DChance: 50 },
        'Arizona' : { ElectoralVotes: 11, RChance : 50, DChance: 50 },
        'North Dakota' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'South Dakota' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'Nebraska' : { ElectoralVotes: 5, RChance : 50, DChance: 50 },
        'Kansas' : { ElectoralVotes: 6, RChance : 50, DChance: 50 },
        'Oklahoma' : { ElectoralVotes: 7, RChance : 50, DChance: 50 },
        'Texas' : { ElectoralVotes: 38, RChance : 50, DChance: 50 },
        'Minnesota' : { ElectoralVotes: 10, RChance : 50, DChance: 50 },
        'Iowa' : { ElectoralVotes: 6, RChance : 50, DChance: 50 },
        'Missouri' : { ElectoralVotes: 10, RChance : 50, DChance: 50 },
        'Arkansas' : { ElectoralVotes: 6, RChance : 50, DChance: 50 },
        'Lousiana' : { ElectoralVotes: 8, RChance : 50, DChance: 50 },
        'Wisconsin' : { ElectoralVotes: 10, RChance : 50, DChance: 50 },
        'Illinois' : { ElectoralVotes: 20, RChance : 50, DChance: 50 },
        'Tennessee' : { ElectoralVotes: 11, RChance : 50, DChance: 50 },
        'Mississippi' : { ElectoralVotes: 6, RChance : 50, DChance: 50 },
        'Alabama' : { ElectoralVotes: 9, RChance : 50, DChance: 50 },
        'Michigan' : { ElectoralVotes: 16, RChance : 50, DChance: 50 },
        'Indiana' : { ElectoralVotes: 11, RChance : 50, DChance: 50 },
        'Kentucky' : { ElectoralVotes: 8, RChance : 50, DChance: 50 },
        'Ohio' : { ElectoralVotes: 18, RChance : 50, DChance: 50 },
        'West Virginia' : { ElectoralVotes: 5, RChance : 50, DChance: 50 },
        'Virginia' : { ElectoralVotes: 13, RChance : 50, DChance: 50 },
        'North Carolina' : { ElectoralVotes: 15, RChance : 50, DChance: 50 },
        'South Carolina' : { ElectoralVotes: 9, RChance : 50, DChance: 50 },
        'Georgia' : { ElectoralVotes: 16, RChance : 50, DChance: 50 },
        'Florida' : { ElectoralVotes: 29, RChance : 50, DChance: 50 },
        'D.C.' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'Maryland' : { ElectoralVotes: 10, RChance : 50, DChance: 50 },
        'Delaware' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'New Jersey' : { ElectoralVotes: 14, RChance : 50, DChance: 50 },
        'Pennsylvania' : { ElectoralVotes: 20, RChance : 50, DChance: 50 },
        'Connectuicut' : { ElectoralVotes: 7, RChance : 50, DChance: 50 },
        'Rhode Island' : { ElectoralVotes: 4, RChance : 50, DChance: 50 },
        'Massachusetts' : { ElectoralVotes: 11, RChance : 50, DChance: 50 },
        'New York' : { ElectoralVotes: 29, RChance : 50, DChance: 50 },
        'Vermont' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'New Hampshire' : { ElectoralVotes: 4, RChance : 50, DChance: 50 },
        'Maine' : { ElectoralVotes: 4, RChance : 50, DChance: 50 },
        'Alaska' : { ElectoralVotes: 3, RChance : 50, DChance: 50 },
        'Hawaii' : { ElectoralVotes: 4, RChance : 50, DChance: 50 }
    };

    const states = Object.keys(dataByState);

    // Helper for using the above map to get a chance of winning
    // from a given poll difference
    const calcWinChance = (diff) => {
        const conv = pollConversion.find((x) =>
            x.DiffRange[0] <= diff && x.DiffRange[1] >= diff
        );
        return conv && conv.ChanceWin;
    }


    // Helper returns true or false depending on whether a given
    // collection of states has enough combined electoral votes
    // to win an election
    const hasSufficientVotes = (states) => {
        const votes = states.reduce((sum,state) =>
            sum += dataByState[state].ElectoralVotes
        , 0);
        return votes >= VOTES_TO_WIN;
    };

    // Helper for getting the combination of states corresponding
    // to the inputted bit pattern i
    const getCombo = (i) => {
        let combo = [];
        for(var j = 0; j < states.length; ++j)
           if((i >> j) & 1)
               combo.push(states[j]);  
        return combo;      
    }

    // To be filled out, combos will be a map of a bit pattern
    // to the corresponding array of state names
    let combos = {};

    // Set time limit on
    const now = new Date();
    const timeout = now.setSeconds(now.getSeconds() + 1); // 1 seconds

    // Run simulation
    const rangetop = Math.pow(2,states.length) + 1;
    while(new Date() < timeout)
    {
        const rand = Math.floor(Math.random() * rangetop);
        if(!combos.hasOwnProperty(rand))
            combos[rand] = getCombo(rand);
    }

    // Sum up the probabilites of the R candidate winning each
    // combination of states that add up to a succifient number
    // of electoral votes
    let RSum = 0;
    const keynums = Object.keys(combos);
    console.log("num combos = " + keynums.length);//TEST
    keynums.forEach((num) => {
     
        const comboStates = combos[num];
     
        // state combo not counted if it doesn't add up
        // to enough electoral votes
        if(!hasSufficientVotes(comboStates))
            return;
     
        // mutltipy together the probabilities of the R
        // winning the state combo
        let RProb = 1;
        comboStates.forEach((state) => {
            RProb *= dataByState[state].RChance / 100;
        });
        const otherStates = states.filter((state) => !comboStates.includes(state));
        otherStates.forEach((state) => {
            RProb *= dataByState[state].DChance / 100;
        });

        RSum += RProb;
    });

    const multiplier = Math.pow(2, states.length + 1) / keynums.length;
    RSum *= multiplier;

    alert("RSum = " + RSum);

     
     
  5. Jul 19, 2016 #4

    chiro

    User Avatar
    Science Advisor

    Hey SlurrerOfSpeech.

    Are you trying to do a probabilistic/statistical estimate?

    If so you could look at doing medians or means with a distribution as opposed to iterating over every outcome and use probabilities to gauge whether an outcome for some group/organization will occur.

    The issue you should have is controlling the variance and depending on the constraints you have, you can shrink them dramatically if the information exists.
     
  6. Jul 24, 2016 #5
    I will try this. Thanks. :)
     
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