# 数据抽取

¥Data Decimation

此示例说明如何使用内置数据抽取来减少图形上绘制的点数以提高性能。

¥This example shows how to use the built-in data decimation to reduce the number of points drawn on the graph for improved performance.

const decimation = {
  enabled: false,
  algorithm: 'min-max',
};const decimation = {
  enabled: false,
  algorithm: 'min-max',
};

const NUM_POINTS = 100000;
Utils.srand(10);
// parseISODate returns a luxon date object to work with in the samples
// We will create points every 30s starting from this point in time
const start = Utils.parseISODate('2021-04-01T00:00:00Z').toMillis();
const pointData = [];
for (let i = 0; i < NUM_POINTS; ++i) {
  // Most data will be in the range [0, 20) but some rare data will be in the range [0, 100)
  const max = Math.random() < 0.001 ? 100 : 20;
  pointData.push({x: start + (i * 30000), y: Utils.rand(0, max)});
}
const data = {
  datasets: [{
    borderColor: Utils.CHART_COLORS.red,
    borderWidth: 1,
    data: pointData,
    label: 'Large Dataset',
    radius: 0,
  }]
};const NUM_POINTS = 100000;
Utils.srand(10);
// parseISODate returns a luxon date object to work with in the samples
// We will create points every 30s starting from this point in time
const start = Utils.parseISODate('2021-04-01T00:00:00Z').toMillis();
const pointData = [];
for (let i = 0; i < NUM_POINTS; ++i) {
  // Most data will be in the range [0, 20) but some rare data will be in the range [0, 100)
  const max = Math.random() < 0.001 ? 100 : 20;
  pointData.push({x: start + (i * 30000), y: Utils.rand(0, max)});
}
const data = {
  datasets: [{
    borderColor: Utils.CHART_COLORS.red,
    borderWidth: 1,
    data: pointData,
    label: 'Large Dataset',
    radius: 0,
  }]
};

const config = {
  type: 'line',
  data: data,
  options: {
    // Turn off animations and data parsing for performance
    animation: false,
    parsing: false,
    interaction: {
      mode: 'nearest',
      axis: 'x',
      intersect: false
    },
    plugins: {
      decimation: decimation,
    },
    scales: {
      x: {
        type: 'time',
        ticks: {
          source: 'auto',
          // Disabled rotation for performance
          maxRotation: 0,
          autoSkip: true,
        }
      }
    }
  }
};const config = {
  type: 'line',
  data: data,
  options: {
    // Turn off animations and data parsing for performance
    animation: false,
    parsing: false,
    interaction: {
      mode: 'nearest',
      axis: 'x',
      intersect: false
    },
    plugins: {
      decimation: decimation,
    },
    scales: {
      x: {
        type: 'time',
        ticks: {
          source: 'auto',
          // Disabled rotation for performance
          maxRotation: 0,
          autoSkip: true,
        }
      }
    }
  }
};

const actions = [
  {
    name: 'No decimation (default)',
    handler(chart) {
      chart.options.plugins.decimation.enabled = false;
      chart.update();
    }
  },
  {
    name: 'min-max decimation',
    handler(chart) {
      chart.options.plugins.decimation.algorithm = 'min-max';
      chart.options.plugins.decimation.enabled = true;
      chart.update();
    },
  },
  {
    name: 'LTTB decimation (50 samples)',
    handler(chart) {
      chart.options.plugins.decimation.algorithm = 'lttb';
      chart.options.plugins.decimation.enabled = true;
      chart.options.plugins.decimation.samples = 50;
      chart.update();
    }
  },
  {
    name: 'LTTB decimation (500 samples)',
    handler(chart) {
      chart.options.plugins.decimation.algorithm = 'lttb';
      chart.options.plugins.decimation.enabled = true;
      chart.options.plugins.decimation.samples = 500;
      chart.update();
    }
  }
];const actions = [
  {
    name: 'No decimation (default)',
    handler(chart) {
      chart.options.plugins.decimation.enabled = false;
      chart.update();
    }
  },
  {
    name: 'min-max decimation',
    handler(chart) {
      chart.options.plugins.decimation.algorithm = 'min-max';
      chart.options.plugins.decimation.enabled = true;
      chart.update();
    },
  },
  {
    name: 'LTTB decimation (50 samples)',
    handler(chart) {
      chart.options.plugins.decimation.algorithm = 'lttb';
      chart.options.plugins.decimation.enabled = true;
      chart.options.plugins.decimation.samples = 50;
      chart.update();
    }
  },
  {
    name: 'LTTB decimation (500 samples)',
    handler(chart) {
      chart.options.plugins.decimation.algorithm = 'lttb';
      chart.options.plugins.decimation.enabled = true;
      chart.options.plugins.decimation.samples = 500;
      chart.update();
    }
  }
];

# 文档

¥Docs