Custom Aggregate Function

You can implement a custom logic for summary calculation within the calculateCustomSummary function. It is called for each summary item whose summaryType is "custom". The function's parameter includes the summaryProcess field that has the following values depending on when the function is called:

  • "start"
    The first call for a summary item. At this stage, initialize the summary item's resulting value.
  • "calculate"
    A call for each data item relating to the summary item. At this stage, modify the summary item's resulting value.
  • "finalize"
    The last call for the summary item. At this stage finalize calculations, for example, format the summary item's resulting value.
jQuery
JavaScript
$(function () {
    $("#dataGridContainer").dxDataGrid({
        // ...
        summary: {
            totalItems: [{
                column: "numericValue",
                summaryType: "custom",
                name: "Mean"
            }, {
                column: "numericValue",
                summaryType: "custom",
                name: "Root Mean Square"
            }],
            calculateCustomSummary: function (e) {
                if (e.name == "Mean") {
                    if (e.summaryProcess == 'start') {
                        e.totalValue = 0; 
                        count1 = 0;
                    } else if (e.summaryProcess == 'calculate') {
                        e.totalValue += e.value;
                        count1++;
                    } else if (e.summaryProcess == 'finalize') {
                        e.totalValue = e.totalValue / count1;
                    }
                }
                if (e.name == "Root Mean Square") {
                    if (e.summaryProcess == 'start') {
                        e.totalValue = 0; 
                        count2 = 0;
                    } else if (e.summaryProcess == 'calculate') {
                        e.totalValue += Math.pow(e.value, 2);
                        count2++;
                    } else if (e.summaryProcess == 'finalize') {
                        e.totalValue = Math.sqrt(e.totalValue / count2);
                    }
                }
            }
        }
    });
});
Angular
HTML
TypeScript
<dx-data-grid ... >
    <dxo-summary [calculateCustomSummary]="calculateMeans">
        <dxi-total-item
            column="numericValue"
            summaryType="custom"
            name="Mean">
        </dxi-total-item>
        <dxi-total-item
            column="numericValue"
            summaryType="custom"
            name="Root Mean Square">
        </dxi-total-item>
    </dxo-summary>
</dx-data-grid>
export class AppComponent {
    calculateMeans (e) {
        if (e.name == "Mean") {
            if (e.summaryProcess == 'start') {
                e.totalValue = 0; 
                count1 = 0;
            } else if (e.summaryProcess == 'calculate') {
                e.totalValue += e.value;
                count1++;
            } else if (e.summaryProcess == 'finalize') {
                e.totalValue = e.totalValue / count1;
            }
        }
        if (e.name == "Root Mean Square") {
            if (e.summaryProcess == 'start') {
                e.totalValue = 0; 
                count2 = 0;
            } else if (e.summaryProcess == 'calculate') {
                e.totalValue += Math.pow(e.value, 2);
                count2++;
            } else if (e.summaryProcess == 'finalize') {
                e.totalValue = Math.sqrt(e.totalValue / count2);
            }
        }
    };
}

The value field of the function's parameter provides access to data, and this data depends on whether you have set the summary item's column field or not. If you have, the data is the value of this column's cell; otherwise, it is the whole data source object.

jQuery
JavaScript
$(function () {
    $("#dataGridContainer").dxDataGrid({
        // ...
        summary: {
            totalItems: [{
                summaryType: "custom",
                name: "SelectedRowsSummary"
            }],
            calculateCustomSummary: function (e) {
                if (e.name === "SelectedRowsSummary") {
                    if (e.summaryProcess === "start") {
                        e.totalValue = 0;
                    } else if (e.summaryProcess === "calculate") {
                        if (e.component.isRowSelected(e.value.ID)) {
                            e.totalValue = e.totalValue + e.value.SaleAmount;
                        }
                    }
                }
            }
        }
    });
});
Angular
HTML
TypeScript
<dx-data-grid ... >
    <dxo-summary [calculateCustomSummary]="calculateCustomSummary">
        <dxi-total-item
            summaryType="custom"
            name="SelectedRowsSummary">
        </dxi-total-item>
    </dxo-summary>
</dx-data-grid>
export class AppComponent {
    calculateCustomSummary (e) {
        if (e.name === "SelectedRowsSummary") {
            if (e.summaryProcess === "start") {
                e.totalValue = 0;
            } else if (e.summaryProcess === "calculate") {
                if (e.component.isRowSelected(e.value.ID)) {
                    e.totalValue = e.totalValue + e.value.SaleAmount;
                }
            }
        }
    };
}

View Demo

See Also