code: function(ratios, len) {
                      if(len === undefined) throw new Error("An error occurred: len was not sent to _getCumulativeProbs");
                      if(ratios.length !== len) throw new Error("Probabilities for sample must be same length as the array to sample from");
  
                      var toReturn = [];
  
                      if(ratios !== undefined) {
                          ratios = this._v(ratios, "a");
                          if(ratios.length !== len) throw new Error("Probabilities array must be the same length as the array you are sampling from");
  
                          var sum = 0;
                          ratios.map(function(ratio) {
                              ratio = this._v(ratio, "nn"); // Note validating as ANY non-negative number
                              sum+= ratio;
                              toReturn.push(sum);
                          }.bind(this));
  
                          // Divide by total to normalize
                          for(var k=0; k<toReturn.length; k++) { toReturn[k] = toReturn[k]/sum; }
                          return toReturn
                      }
                  }
docs: HELPERS 
  
  @param ratios Array of non-negative numbers to be turned into CDF
  @param len length of the collection
  @returns {Array}
  @private