attemps to handle the "Smoothing a graph when there's a drop to zero" issue

thinking about it this option does not make much sense...

curvedLines.js

@@ -65,6 +65,7 @@
  fitPointDist:     int    defines the x axis distance of the additional two points that are used
                           to enforce the min max condition. (you will get curvePointFactor * 3 * |datapoints|
                           "virtual" points if fit is true)
+ smoothZero:       bool   true => smooth joining of the curve with the x-axis when displaying values below zero with a y-axis min of zero
  */
 
 /*
@@ -87,7 +88,8 @@
 				fillColor : null,
 				lineWidth : 2,
 				curvePointFactor : 20,
-				fitPointDist : 0.0001
+				fitPointDist : 0.0001,
+				smoothZero: false
 			}
 		}
 	};
@@ -139,7 +141,14 @@
 						data = series.data;
 					}
 					
-					var points = calculateCurvePoints(data, series.curvedLines);
+
+					//optional smooth out zero passes
+					if (series.curvedLines.smoothZero) {
+						points = calculateZeroSmoothedCurvePoints(data, series.curvedLines);
+					} else {
+						points = calculateCurvePoints(data, series.curvedLines);
+					}
+
 					plotLine(ctx, points, axisx, axisy, series.curvedLines.fill);
 					ctx.restore();
 				}
@@ -167,6 +176,7 @@
 			return ret;
 		}
 
+
 		//nearly the same as in the core library
 		//only ps is adjusted to 2
 		function plotLine(ctx, points, axisx, axisy, fill) {
@@ -258,6 +268,48 @@
 			ctx.stroke();
 		}
 		
+		function calculateZeroSmoothedCurvePoints(data, curvedLinesOptions) {
+	 			var data2 = new Array(new Array, new Array);
+				var Y = 1
+				var X = 0
+
+				var j = 0;
+				for (var i = 0; i < data.length; i++) {
+
+					if (data[i][Y] < 0) {
+						if (i > 0 && data[i-1][Y] > 0) {
+							//point before exists and is over zero
+							var x1 = data[i-1][X];
+							var x2 = data[i][X];
+							var y1 = data[i-1][Y];
+							var y2 = data[i][Y];
+							
+							var newX = ((-y1) / ((y2-y1)/(x2-x1))) + x1;
+							data2[j] = new Array(newX,0);
+							j++;
+						}	
+						data2[j] = new Array(data[i][X],0);
+						j++;				
+						if (i < (data.length-1) && data[i+1][Y] > 0) {
+							//point before exists and is over zero
+							var x1 = data[i][X];
+							var x2 = data[i+1][X];
+							var y1 = data[i][Y];
+							var y2 = data[i+1][Y];
+							
+							var newX = ((-y1) / ((y2-y1)/(x2-x1))) + x1;
+							data2[j] = new Array(newX,0);
+							j++;
+						}													
+					} else {
+						data2[j] = data[i];
+						j++;
+					}
+				}
+								
+				return calculateCurvePoints(data2, curvedLinesOptions);			
+		}
+
 		//no real idea whats going on here code mainly from https://code.google.com/p/flot/issues/detail?id=226
 		//if fit option is selected additional datapoints get inserted before the curve calculations in nergal.dev s code.
 		function calculateCurvePoints(data, curvedLinesOptions) {