MET Calculator for Google Sheet Function

met_calc.js

function MET(type, speed) {

  var STANDING_QUIETLY = 1.3;

  var WALK_MET_TABLE =  [
    [5.0 * 1.6, 8.3],    // 5.0 mph, 8.3 METs
    [4.5 * 1.6, 7.0],    // 4.5 mph, 7.0 METs
    [4.0 * 1.6, 5.0],    // 4.0 mph, 5.0 METs
    [3.5 * 1.6, 4.3],    // 3.5 mph, 4.3 METs
    [2.5 * 1.6, 3.0],    // 2.5 mph, 3.0 METs
    [2.0 * 1.6, 2.8],    // 2.0 mph, 2.8 METs
    [1.7 * 1.6, 2.3],    // 1.7 mph, 2.3 METs
  ];

  var RUN_MET_TABLE = [
    [14.0 * 1.6, 23.0],    // 23.0  14.0 mph (4.3 min/mile)
    [13.0 * 1.6, 19.8],    // 19.8  13.0 mph (4.6 min/mile)
    [12.0 * 1.6, 19.0],    // 19.0  12.0 mph (5 min/mile)
    [11.0 * 1.6, 16.0],    // 16.0  11.0 mph (5.5 min/mile)
    [10.0 * 1.6, 14.5],    // 14.5  10.0 mph (6 min/mile)
    [ 9.0 * 1.6, 12.8],    // 12.8  9.0 mph (6.5 min/mile)
    [ 8.6 * 1.6, 12.3],    // 12.3  8.6 mph (7 min/mile)
    [ 8.0 * 1.6, 11.8],    // 11.8  8.0 mph (7.5 min/mile)
    [ 7.5 * 1.6, 11.8],    // 11.8  7.5 mph (8 min/mile)
    [ 7.0 * 1.6, 11.0],    // 11.0  7.0 mph (8.5 min/mile)
    [ 6.7 * 1.6, 10.5],    // 10.5  6.7 mph (9 min/mile)
    [ 6.0 * 1.6,  9.8],    // 9.8   6.0 mph (10 min/mile)
    [ 5.2 * 1.6,  9.0],    // 9.0   5.2 mph (11.5 min/mile)
    [ 5.0 * 1.6,  8.3],    // 8.3   5.0 mph (12 min/mile)
    [ 4.0 * 1.6,  6.0],    // 6.0   4.0 mph (15 min/mile)
  ];

  var BICYCLE_MET_TABLE = [
    [20.0 * 1.6, 15.8],  // 20 mph, 15.8 METs
    [16.0 * 1.6, 12.0],  // 16 mph, 12 METs
    [14.0 * 1.6, 10.0],  // 14 mph, 10 METs
    [12.0 * 1.6,  8.0],  // 12 mph, 8 METs
    [10.0 * 1.6,  6.8],  // 10 mph, 6.8 METs
    [ 9.4 * 1.6,  5.8],  // 9.4 mph, 5.8 METs
    [ 5.5 * 1.6,  3.5],  // 5.5 mph, 3.5 METs
  ];

  var metTable = null;
  switch (type) {
    case "Run":
      metTable = RUN_MET_TABLE;
      break;
    case "Walk":
      metTable = WALK_MET_TABLE;
      break;
    case "Bike":
      metTable = BICYCLE_MET_TABLE;
      break;
    default:
      metTable = WALK_MET_TABLE;
      break;
  }

  function getMetBetween(speed, level, nextLevel) {
    return level[1] + (speed - level[0]) * (nextLevel[1] - level[1]) / (nextLevel[0] - level[0]);
  }

  var met = 0;
  for (var i = 0; i < metTable.length; i++) {
    var level = metTable[i];
    if (speed >= level[0]) {
      if (i == 0) {
        met = level[1];
      } else {
          var nextLevel = metTable[i - 1];
        met = getMetBetween(speed, level, nextLevel);
      }
      break;
    }
  }

  var minLevel = metTable[metTable.length - 1];
  if (speed < minLevel[0]) {
      var level = [0, STANDING_QUIETLY];
      met = getMetBetween(speed, level, minLevel);
  }

  return met;
}