code: function fromStepping ( xVal, xPct, value ) {
  
          // There is no range group that fits 100
          if ( value >= 100 ){
              return xVal.slice(-1)[0];
          }
  
          var j = getJ( value, xPct ), va, vb, pa, pb;
  
          va = xVal[j-1];
          vb = xVal[j];
          pa = xPct[j-1];
          pb = xPct[j];
  
          return isPercentage([va, vb], (value - pa) * subRangeRatio (pa, pb));
      }
docs: (value) Input a percentage, find where it is on the specified range.