echarts dataSample 源码
echarts dataSample 代码
文件路径:/src/processor/dataSample.ts
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
import { StageHandler, SeriesOption, SeriesSamplingOptionMixin } from '../util/types';
import { Dictionary } from 'zrender/src/core/types';
import SeriesModel from '../model/Series';
import { isFunction, isString } from 'zrender/src/core/util';
type Sampler = (frame: ArrayLike<number>) => number;
const samplers: Dictionary<Sampler> = {
average: function (frame) {
let sum = 0;
let count = 0;
for (let i = 0; i < frame.length; i++) {
if (!isNaN(frame[i])) {
sum += frame[i];
count++;
}
}
// Return NaN if count is 0
return count === 0 ? NaN : sum / count;
},
sum: function (frame) {
let sum = 0;
for (let i = 0; i < frame.length; i++) {
// Ignore NaN
sum += frame[i] || 0;
}
return sum;
},
max: function (frame) {
let max = -Infinity;
for (let i = 0; i < frame.length; i++) {
frame[i] > max && (max = frame[i]);
}
// NaN will cause illegal axis extent.
return isFinite(max) ? max : NaN;
},
min: function (frame) {
let min = Infinity;
for (let i = 0; i < frame.length; i++) {
frame[i] < min && (min = frame[i]);
}
// NaN will cause illegal axis extent.
return isFinite(min) ? min : NaN;
},
// TODO
// Median
nearest: function (frame) {
return frame[0];
}
};
const indexSampler = function (frame: ArrayLike<number>) {
return Math.round(frame.length / 2);
};
export default function dataSample(seriesType: string): StageHandler {
return {
seriesType: seriesType,
// FIXME:TS never used, so comment it
// modifyOutputEnd: true,
reset: function (seriesModel: SeriesModel<SeriesOption & SeriesSamplingOptionMixin>, ecModel, api) {
const data = seriesModel.getData();
const sampling = seriesModel.get('sampling');
const coordSys = seriesModel.coordinateSystem;
const count = data.count();
// Only cartesian2d support down sampling. Disable it when there is few data.
if (count > 10 && coordSys.type === 'cartesian2d' && sampling) {
const baseAxis = coordSys.getBaseAxis();
const valueAxis = coordSys.getOtherAxis(baseAxis);
const extent = baseAxis.getExtent();
const dpr = api.getDevicePixelRatio();
// Coordinste system has been resized
const size = Math.abs(extent[1] - extent[0]) * (dpr || 1);
const rate = Math.round(count / size);
if (isFinite(rate) && rate > 1) {
if (sampling === 'lttb') {
seriesModel.setData(data.lttbDownSample(data.mapDimension(valueAxis.dim), 1 / rate));
}
let sampler;
if (isString(sampling)) {
sampler = samplers[sampling];
}
else if (isFunction(sampling)) {
sampler = sampling;
}
if (sampler) {
// Only support sample the first dim mapped from value axis.
seriesModel.setData(data.downSample(
data.mapDimension(valueAxis.dim), 1 / rate, sampler, indexSampler
));
}
}
}
}
};
}
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