Similarity / Cosinus computation

simil_cos.js

var simil = related_top.map(function(rel_top) {
  var product = rel_top.map(function(v, i) {
    return v * hashtag_top[i];
  }).reduce(function(prev, curr) {
    return prev + curr;
  });

  var norm_x = Math.sqrt(rel_top.map(function(v, i) {
    return v * v;
  }).reduce(function(prev, curr) {
    return prev + curr;
  }));

  var norm_y = Math.sqrt(hashtag_top.map(function(v, i) {
    return v * v;
  }).reduce(function(prev, curr) {
    return prev + curr;
  }));

  return product / (norm_x * norm_y);
});