Fix #1370, 添加数据抽希策略配置

apache · Mar 21, 2015 · e05c812 · e05c812
1 parent fe43881
commit e05c812
Showing 1 changed file with 72 additions and 5 deletions.
diff --git a/src/chart/line.js b/src/chart/line.js
@@ -27,6 +27,8 @@ define(function (require) {
         // stack: null
         xAxisIndex: 0,
         yAxisIndex: 0,
+        // 'nearest', 'min', 'max', 'average'
+        dataFilter: 'nearest',
         itemStyle: {
             normal: {
                 // color: 各异,
@@ -516,9 +518,11 @@ define(function (require) {
                         }
                         else {
                             // 大数据模式截取pointList
-                            singlePL = this._getLargePointList(orient, singlePL);
+                            singlePL = this._getLargePointList(
+                                orient, singlePL, serie.dataFilter
+                            );
                         }
-                        
+
                         // 折线图
                         var polylineShape = new PolylineShape({
                             zlevel: this.getZlevelBase(),
@@ -647,7 +651,7 @@ define(function (require) {
         /**
          * 大规模pointList优化 
          */
-        _getLargePointList: function(orient, singlePL) {
+        _getLargePointList: function(orient, singlePL, filter) {
             var total;
             if (orient === 'horizontal') {
                 total = this.component.grid.getWidth();
@@ -658,12 +662,75 @@ define(function (require) {
 
             var len = singlePL.length;
             var newList = [];
+
+            if (typeof(filter) != 'function') {
+                switch (filter) {
+                    case 'min':
+                        filter = function (arr) {
+                            return Math.max.apply(null, arr);
+                        };
+                        break;
+                    case 'max':
+                        filter = function (arr) {
+                            return Math.min.apply(null, arr);
+                        };
+                        break;
+                    case 'average':
+                        filter = function (arr) {
+                            var total = 0;
+                            for (var i = 0; i < arr.length; i++) {
+                                total += arr[i];
+                            }
+                            return total / arr.length;
+                        };
+                        break;
+                    default:
+                        filter = function (arr) {
+                            return arr[0];
+                        }
+                }
+            }
+
+            var windowData = [];
             for (var i = 0; i < total; i++) {
-                newList[i] = singlePL[Math.floor(len / total * i)];
+                var idx0 = Math.floor(len / total * i);
+                var idx1 = Math.min(Math.floor(len / total * (i + 1)), len);
+                if (idx1 <= idx0) {
+                    continue;
+                }
+
+                for (var j = idx0; j < idx1; j++) {
+                    windowData[j - idx0] = orient === 'horizontal'
+                        ? singlePL[j][1] : singlePL[j][0];
+                }
+
+                windowData.length = idx1 - idx0;
+                var filteredVal = filter(windowData);
+                var nearestIdx = -1;
+                var minDist = Infinity;
+                // 寻找值最相似的点，使用其其它属性
+                for (var j = idx0; j < idx1; j++) {
+                    var val = orient === 'horizontal'
+                        ? singlePL[j][1] : singlePL[j][0];
+                    var dist = Math.abs(val - filteredVal);
+                    if (dist < minDist) {
+                        nearestIdx = j;
+                        minDist = dist;
+                    }
+                }
+
+                var newItem = singlePL[nearestIdx].slice();
+                if (orient === 'horizontal') {
+                    newItem[1] = filteredVal;
+                }
+                else {
+                    newItem[0] = filteredVal;
+                }
+                newList.push(newItem);
             }
             return newList;
         },
-        
+
         _getSmooth: function (isSmooth/*, pointList, orient*/) {
             if (isSmooth) {
                 /* 不科学啊，发现0.3通用了