无法使用series.sampling选项, 使用后就会抛出异常

[qqj1228]

One-line summary [问题简述]

无法使用series.sampling选项, 使用后就会抛出异常

Version & Environment [版本及环境]

• ECharts version [ECharts 版本]: 3.8.5
• Browser version [浏览器类型和版本]: Chrome, 59.0.3071.115
• OS Version [操作系统类型和版本]: win10 pro, 1709, 16299.309
  另外我是在electron环境里运行的，electron版本：1.8.3

Expected behaviour [期望结果]

可以正常使用series.sampling选项

ECharts option [ECharts配置项]

// 这是初始化option，运行时会再传入下面的option
option = {
        legend: {
            data: ['盖侧', '轴侧'],
        },
        grid: [{
            top: '10%',
            height: '24%',
            left: '5%',
            right: '5%',
        }, {
            top: '40%',
            height: '24%',
            left: '5%',
            right: '5%',
        }, {
            top: '70%',
            height: '24%',
            left: '5%',
            right: '5%',
        }],
        xAxis: [{
            type: 'value',
            name: 'θ°',
            axisPointer: {triggerTooltip: false},
            min: 0,
            max: 360,
            splitNumber: 6,
            minInterval: 60,
            maxInterval: 180,
        }, {
            gridIndex: 1,
            type: 'value',
            name: 'θ°',
            axisPointer: {triggerTooltip: false},
            min: 0,
            max: 360,
            splitNumber: 6,
            minInterval: 60,
            maxInterval: 180,
        }, {
            gridIndex: 2,
            type: 'value',
            name: 'θ°',
            axisPointer: {triggerTooltip: false},
            min: 0,
            max: 360,
            splitNumber: 6,
            minInterval: 60,
            maxInterval: 180,
        }],
        yAxis: [{
            type: 'value',
            name: 'h(mm)',
            nameLocation: 'middle',
            nameGap: 30,
        }, {
            gridIndex: 1,
            type: 'value',
            name: 'v(m/s)',
            nameLocation: 'middle',
            nameGap: 30,
        }, {
            gridIndex: 2,
            type: 'value',
            name: 'p(MPa)',
            nameLocation: 'middle',
            nameGap: 30,
        }],
        series: [{
            name: '盖侧',
            type: 'line',
            showSymbol: false,
            sampling: 'max',                          // <===============sampling选项
            dimensions: ['theta', 'h', 'v', 'p'],
            encode: {
                x: 'theta',
                y: 'h',
                tooltip: ['h', 'v', 'p'],
            },
        }, {
            name: '盖侧',
            type: 'line',
            xAxisIndex: 1,
            yAxisIndex: 1,
            showSymbol: false,
            tooltip: {show: false},
            dimensions: ['theta', 'h', 'v', 'p'],
            encode: {
                x: 'theta',
                y: 'v',
            },
        }, {
            name: '盖侧',
            type: 'line',
            xAxisIndex: 2,
            yAxisIndex: 2,
            showSymbol: false,
            tooltip: {show: false},
            dimensions: ['theta', 'h', 'v', 'p'],
            encode: {
                x: 'theta',
                y: 'p',
            },
        }, {
            name: '轴侧',
            type: 'line',
            showSymbol: false,
            dimensions: ['theta', 'h', 'v', 'p'],
            encode: {
                x: 'theta',
                y: 'h',
                tooltip: ['h', 'v', 'p'],
            },
        }, {
            name: '轴侧',
            type: 'line',
            xAxisIndex: 1,
            yAxisIndex: 1,
            showSymbol: false,
            tooltip: {show: false},
            dimensions: ['theta', 'h', 'v', 'p'],
            encode: {
                x: 'theta',
                y: 'v',
            },
        }, {
            name: '轴侧',
            type: 'line',
            xAxisIndex: 2,
            yAxisIndex: 2,
            showSymbol: false,
            tooltip: {show: false},
            dimensions: ['theta', 'h', 'v', 'p'],
            encode: {
                x: 'theta',
                y: 'p',
            },
        }],
}

// 运行时再传入该option
    const option = {
        tooltip: {trigger: 'axis'},
        axisPointer: {
            link: {xAxisIndex: 'all'},
        },
        series: [{
            data: plotData.head,
        }, {
            data: plotData.head,
        }, {
            data: plotData.head,
        }, {
            data: plotData.crank,
        }, {
            data: plotData.crank,
        }, {
            data: plotData.crank,
        }],
    };

// 绘图数据, 每个数组含有大概4000~5000个数据点
plotData = {
    head: ['theta', 'h', 'v', 'p'],
    crank: ['theta', 'h', 'v', 'p'],
}

Other comments [其他信息]

运行时会报错：TypeError: Cannot read property 'length' of undefined
是在lib/data/list.js文件内的listProto.downSample函数出错，第900行

listProto.downSample = function (dimension, rate, sampleValue, sampleIndex) {
  var list = cloneListForMapAndSample(this, [dimension]);
  var storage = this._storage;
  var targetStorage = list._storage;
  var originalIndices = this.indices;
  var indices = list.indices = [];
  var frameValues = [];
  var frameIndices = [];
  var frameSize = Math.floor(1 / rate);
  var dimStore = targetStorage[dimension];
  var len = this.count(); // Copy data from original data

  for (var i = 0; i < storage[dimension].length; i++) {         // <======就是这句
    targetStorage[dimension][i] = storage[dimension][i];
  }

上面的storage[dimension].length里dimension是"Y"，但是storage里只有{theta: [], h: [], v: [], p: []}
也就是说dimension应该是"h"而不是"Y"。

[qqj1228]

简单跟踪了一下，文件：lib/processor/dataSample.js，第79行

function _default(seriesType, ecModel, api) {
  ecModel.eachSeriesByType(seriesType, function (seriesModel) {
    var data = seriesModel.getData();
    var sampling = seriesModel.get('sampling');
    var coordSys = seriesModel.coordinateSystem; // Only cartesian2d support down sampling

    if (coordSys.type === 'cartesian2d' && sampling) {
      var baseAxis = coordSys.getBaseAxis();
      var valueAxis = coordSys.getOtherAxis(baseAxis);  // <====该函数返回的就是valueAxis.dim
      var extent = baseAxis.getExtent(); // Coordinste system has been resized

      var size = extent[1] - extent[0];
      var rate = Math.round(data.count() / size);

      if (rate > 1) {
        var sampler;

        if (typeof sampling === 'string') {
          sampler = samplers[sampling];
        } else if (typeof sampling === 'function') {
          sampler = sampling;
        }

        if (sampler) {
          data = data.downSample(valueAxis.dim, 1 / rate, sampler, indexSampler); // 调用参数不对
          seriesModel.setData(data);
        }
      }
    }
  }, this);
}

上面注释的那句调用data.downSample函数的第一个参数valueAxis.dim有问题，其值为"Y"
var valueAxis = coordSys.getOtherAxis(baseAxis);直接把valueAxis.dim赋值为"Y"
lib/coord/cartesian/Cartesian2D.js第75行

  /**
   * Get other axis
   * @param {module:echarts/coord/cartesian/Axis2D} axis
   */
  getOtherAxis: function (axis) {
    return this.getAxis(axis.dim === 'x' ? 'y' : 'x');
  }

按照我的理解不是应该把encode里的"Y"映射成"h"吗？