Multiple Linear Regression

// Function used to get best fit. See http://www.varsitytutors.com/hotmath/hotmath_help/topics/line-of-best-fit.html for formula
function LOBF(data, xiden, yiden) {
  let Xsum = 0, Ysum = 0, Xmean = 0, Ymean = 0;

  for (let i = 0; i < data.length; i++) {
    let point = data[i];
    Xsum += point[xiden];
    Ysum += point[yiden];
  }

  Xmean = Xsum / data.length;
  Ymean = Ysum / data.length;

  let top = 0, bottom = 0;
  for (let i = 0; i < data.length; i++) {
    point = data[i];
    top += (point[xiden] - Xmean) * (point[yiden] - Ymean);
    bottom += Math.pow((point[xiden] - Xmean), 2);
  }

  return top / bottom;
}

let data = [
  {milesTraveled: 80, numDeliveries:4, gasPrice : 3.84, travelTime: 7},
  {milesTraveled: 66, numDeliveries:1, gasPrice : 3.19, travelTime: 5.4},
  {milesTraveled: 78, numDeliveries:3, gasPrice : 3.78, travelTime: 6.6},
  {milesTraveled: 111, numDeliveries:6, gasPrice : 3.89, travelTime: 7.4},
  {milesTraveled: 44, numDeliveries:1, gasPrice : 3.57, travelTime: 4.8},
  {milesTraveled: 77, numDeliveries:3, gasPrice : 3.57, travelTime: 6.4},
  {milesTraveled: 80, numDeliveries:3, gasPrice : 3.03, travelTime: 7},
  {milesTraveled: 66, numDeliveries:2, gasPrice : 3.51, travelTime: 5.6},
  {milesTraveled: 109, numDeliveries:5, gasPrice : 3.54, travelTime: 7.3},
  {milesTraveled: 76, numDeliveries:3, gasPrice : 3.25, travelTime: 6.4},
];

let slopes = {
  milesTraveled: {
    travelTime : 0,
    numDeliveries: 0,
    gasPrice     : 0
  },
  numDeliveries: {
    travelTime : 0,
    milesTraveled: 0,
    gasPrice     : 0
  },
  gasPrice     : {
    travelTime : 0,
    numDeliveries: 0,
    milesTraveled: 0
  }
};

let SSE = {
  milesTraveled: {
    travelTime : 0,
    numDeliveries: 0,
    gasPrice     : 0
  },
  numDeliveries: {
    travelTime : 0,
    milesTraveled: 0,
    gasPrice     : 0
  },
  gasPrice     : {
    travelTime : 0,
    numDeliveries: 0,
    milesTraveled: 0
  }
};


// Calculate the slopes
slopes.milesTraveled.travelTime    = LOBF(data, 'milesTraveled', 'travelTime');
slopes.milesTraveled.numDeliveries = LOBF(data, 'milesTraveled', 'numDeliveries');
slopes.milesTraveled.gasPrice      = LOBF(data, 'milesTraveled', 'gasPrice');

slopes.numDeliveries.travelTime    = LOBF(data, 'numDeliveries', 'travelTime');
slopes.numDeliveries.milesTraveled = LOBF(data, 'numDeliveries', 'milesTraveled');
slopes.numDeliveries.gasPrice      = LOBF(data, 'numDeliveries', 'gasPrice');

slopes.gasPrice.travelTime         = LOBF(data, 'gasPrice' , 'travelTime');
slopes.gasPrice.milesTraveled      = LOBF(data, 'gasPrice' , 'milesTraveled');
slopes.gasPrice.numDeliveries      = LOBF(data, 'gasPrice' , 'numDeliveries');

// Calculate the SSE
for (let i = 0; i < data.length; i++) {
  let delivery = data[i];

  SSE.milesTraveled.travelTime    += Math.pow(delivery.travelTime    - (delivery.milesTraveled * slopes.milesTraveled.travelTime),2);
  SSE.milesTraveled.numDeliveries += Math.pow(delivery.numDeliveries - (delivery.milesTraveled * slopes.milesTraveled.numDeliveries),2);
  SSE.milesTraveled.gasPrice      += Math.pow(delivery.gasPrice      - (delivery.milesTraveled * slopes.milesTraveled.gasPrice),2);

  SSE.numDeliveries.travelTime    += Math.pow(delivery.travelTime    - (delivery.numDeliveries  * slopes.numDeliveries.travelTime),2);
  SSE.numDeliveries.milesTraveled += Math.pow(delivery.milesTraveled - (delivery.numDeliveries  * slopes.numDeliveries.milesTraveled),2);
  SSE.numDeliveries.gasPrice      += Math.pow(delivery.gasPrice      - (delivery.numDeliveries  * slopes.numDeliveries.gasPrice),2);

  SSE.gasPrice.travelTime         += Math.pow(delivery.travelTime    - (delivery.gasPrice       * slopes.gasPrice.travelTime),2);
  SSE.gasPrice.numDeliveries      += Math.pow(delivery.numDeliveries - (delivery.gasPrice       * slopes.gasPrice.numDeliveries),2);
  SSE.gasPrice.milesTraveled      += Math.pow(delivery.milesTraveled - (delivery.gasPrice       * slopes.gasPrice.milesTraveled),2);
}
console.log(`
 — Multiple Linear Regression — 
 SUMS:
 ${JSON.stringify(sums)}
 — — — — — — — — — — — — — — — -
 Slopes:
 ${JSON.stringify(slopes)}
 — — — — — — — — — — — — — — — -
 SSE:
 ${JSON.stringify(SSE)}
`);