index.js

var snap = require("./js/snap.svg-min.js");
var under = require("./js/underscore-min.js");

function getRandom (weights, values) {
    var num = Math.random(),
        s = 0,
        lastIndex = weights.length - 1;
    for (var i = 0; i < lastIndex; ++i) {
        s += weights[i];
        if (num < s) {
            return values[i];
        }
      }
return values[lastIndex];
};

var text_oryg = new String("Out beyond ideas of wrongdoing and rightdoing there is a field. \
I will meet you there. When the soul lies down in that grass the world is too full to talk about");
var text_t = text_oryg.replace(/\./g, "");
var text = text_t.replace(/\s/g, "");

function charCount(str) {
  return under._(str.split('')).countBy(function(char) {
    //console.log(char);
    return char.toLowerCase();
  });
}

function wordCount(str) {
  return _(str.split(' ')).countBy(function(char) {
    return char.replace(/\./g, "").toLowerCase();
  });
}

function getCharacter() {
    return String.fromCharCode(65+Math.floor((Math.random()*26)));
}
function sum(o){
    for(var s = 0, i = o.length; i; s += o[--i]);
    return s;
};

var s = charCount(text);
var weights = [];
var letters = [];

for (var key in s) {
  weights.push(s[key]);
  letters.push(key);
}
var w_sum = sum(weights);
var weighted_prob = weights.map(function(x){return x / w_sum});


var width = 320;
var height = 320;
var cols = 4;
var rows = 4;
var s = snap.Snap("14in","12in");
snap.Snap.load("tiles.svg", function (f) {
          var g = f.select("g");
          s.append(g);
          for ( i=0; i<cols; i++) {
             for ( j=0; j<rows; j++) {
                if (i || j ) {   // skip the first cell
                   var h = g.clone();
                   var x = i*width+10;
                   var y = j*height+30;
                   var tstr = "translate("+x+","+y+")";
                   h.transform(tstr);

                   $( "tspan" ).each(function( index ) {
                         //$(this).text(getCharacter());
                         $(this).text(getRandom (weighted_prob, letters));
                     });
                }
             }
          }
      });