 proportional padding to be added below the chart. for 10% padding, specify 1.1.
   *   yRangeFunction: undefined,                // function({min: , max: }) { return {min: , max: }; }
   *   scaleSmoothing: 0.125,                    // controls the rate at which y-value zoom animation occurs
   *   millisPerPixel: 20,                       // sets the speed at which the chart pans by
   *   enableDpiScaling: true,                   // support rendering at different DPI depending on the device
   *   yMinFo