DevExtreme React - Data Aggregation

If the Chart contains many series points, displaying all of them may slow down its performance. In this case, it is better to aggregate the series points or replace a group of them with a single point. This aggregated series point conveys a summary of several points, which also facilitates analysis of large datasets. This article discusses steps to configure data aggregation in the Chart.

Multiple Series Demo Financial Series Demo

You can enable data aggregation for individual series, all series of a specific type, or for all series in the Chart. The following code demonstrates all the three cases:

$(function() {
    $("#chartContainer").dxChart({
        // ...
        commonSeriesSettings: {
            // Enables data aggregation for all series in the Chart
            aggregation: {
                enabled: true
            },
            fullstackedbar: {
                // Enables data aggregation for all Full-Stacked Bar series
                aggregation: {
                    enabled: true
                }
            }
        },
        series: [{
            // Enables data aggregation for an individual series
            aggregation: {
                enabled: true
            }
        }, {
            // ...
        }]
    });
});

<dx-chart ... >
    <dxo-common-series-settings>
        <!-- Enables data aggregation for all series in the Chart -->
        <dxo-aggregation
            [enabled]="true">
        </dxo-aggregation>

        <dxo-fullstackedbar>
            <!-- Enables data aggregation for all Full-Stacked Bar series -->
            <dxo-aggregation
                [enabled]="true">
            </dxo-aggregation>
        </dxo-fullstackedbar>

    </dxo-common-series-settings>

    <dxi-series>
        <!-- Enables data aggregation for an individual series -->
        <dxo-aggregation
            [enabled]="true">
        </dxo-aggregation>
    </dxi-series>
</dx-chart>

import { DxChartModule } from "devextreme-angular";
// ...
export class AppComponent {
    // ...
}
@NgModule({
    imports: [
        // ...
        DxChartModule
    ],
    // ...
})

Series points are grouped for aggregation using intervals: those points that fall within the same interval on the argument axis get aggregated together. You can specify the length of the intervals in axis units (numbers or dates), in pixels, or aggregate points by categories:

• Axis units (for continuous and logarithmic axes only)
  Use the argumentAxis.aggregationInterval option.

  jQuery

  JavaScript

  $(function() {
      $("#chartContainer").dxChart({
          // ...
          argumentAxis: {
              // A new interval every 100 units
              aggregationInterval: 100,
              // A new interval every day
              aggregationInterval: "day",
              // A new interval every five days
              aggregationInterval: { days: 5 }
          }
      });
  });

  Angular

  HTML

  TypeScript

  <dx-chart ... >
      <dxo-argument-axis
          [aggregationInterval]="100"  <!-- A new interval every 100 units -->
          aggregationInterval="day"> <!-- A new interval every day -->
          <dxo-aggregation-interval
              [days]="5">            <!-- A new interval every five days -->
          </dxo-aggregation-interval>
      </dxo-argument-axis>
  </dx-chart>

  import { DxChartModule } from "devextreme-angular";
  // ...
  export class AppComponent {
      // ...
  }
  @NgModule({
      imports: [
          // ...
          DxChartModule
      ],
      // ...
  })

• Pixels
  Use the argumentAxis.aggregationGroupWidth option.

  jQuery

  JavaScript

  $(function() {
      $("#chartContainer").dxChart({
          // ...
          argumentAxis: {
              // A new interval every 100 pixels
              aggregationGroupWidth: 100
          }
      });
  });

  Angular

  HTML

  TypeScript

  <dx-chart ... >
      <dxo-argument-axis
          [aggregationGroupWidth]="100"> <!-- A new interval every 100 pixels -->
      </dxo-argument-axis>
  </dx-chart>

  import { DxChartModule } from "devextreme-angular";
  // ...
  export class AppComponent {
      // ...
  }
  @NgModule({
      imports: [
          // ...
          DxChartModule
      ],
      // ...
  })

• Categories
  Aggregation by categories can be applied only when the axis displays categories, and each category contains two or more points. To apply it, set argumentAxis.aggregateByCategory to true:

  jQuery

  JavaScript

  $(function() {
      $("#chartContainer").dxChart({
          // ...
          argumentAxis: {
              aggregateByCategory: true
          }
      });
  });

  Angular

  HTML

  TypeScript

  <dx-chart ... >
      <dxo-argument-axis
          [aggregateByCategory]="true">
      </dxo-argument-axis>
  </dx-chart>

  import { DxChartModule } from "devextreme-angular";
  // ...
  export class AppComponent {
      // ...
  }
  @NgModule({
      imports: [
          // ...
          DxChartModule
      ],
      // ...
  })

Aggregation methods specify how series points should be aggregated. DevExtreme provides the most commonly used aggregation methods out of the box. To use one, specify a series' aggregation.method option. In its description, you will find the full list of provided aggregation methods. Note that different series types have different aggregation methods available.

The following code shows how to specify aggregation methods for each series individually. Data aggregation is enabled for all series in the commonSeriesSettings object.

$(function() {
    $("#chartContainer").dxChart({
        // ...
        commonSeriesSettings: {
            aggregation: {
                enabled: true
            }
        },
        series: [{
            // ...
            type: "line",
            aggregation: {
                method: "min"
            }
        }, {
            // ...
            type: "bar",
            aggregation: {
                method: "max"
            }
        }]
    });
});

<dx-chart ... >
    <dxo-common-series-settings ... >
        <dxo-aggregation
            [enabled]="true">
        </dxo-aggregation>
    </dxo-common-series-settings>

    <dxi-series type="line" ... >
        <dxo-aggregation
            method="min">
        </dxo-aggregation>
    </dxi-series>

    <dxi-series type="bar" ... >
        <dxo-aggregation
            method="max">
        </dxo-aggregation>
    </dxi-series>
</dx-chart>

import { DxChartModule } from "devextreme-angular";
// ...
export class AppComponent {
    // ...
}
@NgModule({
    imports: [
        // ...
        DxChartModule
    ],
    // ...
})

View Demo

You can implement a custom aggregate function instead of using an out-of-the-box aggregation method.

When implementing a custom aggregate function, use the aggregationInfo object that is passed to it as the first argument. This object contains information on the aggregation interval for which the function is called and the data objects that fall within this interval. In addition, you can access the Series object, which is passed to the function as the second argument.

To apply the function, assign it to the series' aggregation.calculate option and set the aggregation.method option to "custom".

View Demo

In the following code, a custom aggregation function implements the median filter algorithm:

$(function() {
    $("#chartContainer").dxChart({
        dataSource: [
            { argument: 1, value: 10 },
            // ...
        ],
        series: [{
            argumentField: "argument",
            valueField: "value",
            aggregation: {
                enabled: true,
                method: "custom",
                calculate: function (aggregationInfo) {
                    if (aggregationInfo.data.length) {
                        return {
                            argument: aggregationInfo.intervalStart,
                            value: aggregationInfo.data[Math.floor(aggregationInfo.data.length / 2)].value
                        };
                    }
                }

            }
        }]
    });
});

<dx-chart [dataSource]="data">
    <dxi-series
        argumentField="argument"
        valueField="value">
        <dxo-aggregation
            [enabled]="true"
            method="custom"
            [calculate]="calcMedianFilter">
        </dxo-aggregation>
    </dxi-series>
</dx-chart>

import { DxChartModule } from "devextreme-angular";
// ...
export class AppComponent {
    data = [
        { argument: 1, value: 10 },
        // ...
    ];
    calcMedianFilter (aggregationInfo) {
        if (aggregationInfo.data.length) {
            return {
                argument: aggregationInfo.intervalStart,
                value: aggregationInfo.data[Math.floor(aggregationInfo.data.length / 2)].value
            };
        }
    };
}
@NgModule({
    imports: [
        // ...
        DxChartModule
    ],
    // ...
})