Eu estou usando os amcharts 4 e queria usar meus dados aninhados, sei que os amcharts não suportam dados aninhados, então adicionei um evento no parseended para alterar a estrutura do meu json. Posso obter o ID do evento, mas não posso adicionar os dados da matriz no objeto. Posso ver com meu depurador que ele realmente passa por cada objeto da matriz aninhada, mas ele não os adiciona ao objeto newDataItem.

Meu JSON:

{{
  "Event": {
    "@id": "45",
    "@name": "SP:StmtCompleted",
    "Column": [
      {
        "@id": "1",
        "@name": "TextData",
        "#text": "SELECT [Object Timestamp], [Object Type], [Object ID], [Change Type] FROM \"test\".dbo.\"Object Tracking\" WITH(TABLOCK) WHERE [Object Timestamp] > @lastKnownTimeStamp"
      },
      {
        "@id": "3",
        "@name": "DatabaseID",
        "#text": "24"
      },
      {
        "@id": "11",
        "@name": "LoginName",
        "#text": "test\\MBS_SERVER-NAV03"
      },
      {
        "@id": "4",
        "@name": "TransactionID",
        "#text": "206618305"
      },
      {
        "@id": "12",
        "@name": "S,PID",
        "#text": "77"
      },
      {
        "@id": "10",
        "@name": "ApplicationName",
        "#text": "Microsoft Dynamics NAV Service"
      },
      {
        "@id": "13",
        "@name": "Duration",
        "#text": "25"
      },
      {
        "@id": "14",
        "@name": "StartTime",
        "#text": "2018-09-05T10:24:20.83+02:00"
      },
      {
        "@id": "15",
        "@name": "EndTime",
        "#text": "2018-09-05T10:24:20.83+02:00"
      },
      {
        "@id": "16",
        "@name": "Reads",
        "#text": "2"
      },
      {
        "@id": "17",
        "@name": "Writes",
        "#text": "0"
      },
      {
        "@id": "18",
        "@name": "CPU",
        "#text": "0"
      },
      {
        "@id": "28",
        "@name": "ObjectType",
        "#text": "20816"
      },
      {
        "@id": "35",
        "@name": "DatabaseName",
        "#text": "test"
      },
      {
        "@id": "48",
        "@name": "RowCounts",
        "#text": "0"
      }
    ]
  }
}}

Um exemplo do resultado que tento alcançar

{
  "_id": "45",
  "TransactionID": "4",
  "SPID": "12"
  ....
  ....
}

Meu componente .ts:

import { Component, NgZone } from '@angular/core';
import * as am4core from "@amcharts/amcharts4/core";
import * as am4charts from "@amcharts/amcharts4/charts";
import am4themes_animated from "@amcharts/amcharts4/themes/animated";
import { DataSource } from '@amcharts/amcharts4/core';
import { forEach } from '@angular/router/src/utils/collection';

am4core.useTheme(am4themes_animated);

@Component({
  selector: 'app-chart',
  templateUrl: './chart.component.html',
  styleUrls: ['./chart.component.css']
})

export class ChartComponent {
  constructor(private zone: NgZone) { }

  ngAfterViewInit() {
    this.zone.runOutsideAngular(() => {
      let chart = am4core.create("chartdiv", am4charts.XYChart)

      chart.paddingRight = 30;
      chart.dateFormatter.inputDateFormat = "yyyy-MM-dd HH:mm";

      var colorSet = new am4core.ColorSet();
      colorSet.saturation = 0.4;
      chart.dataSource.url = "https://localhost:44321/api/upload/readFile";
      chart.dataSource.events.on("parseended", function (ev) {
        // parsed data is assigned to data source's `data` property
        var data = ev.target.data;
        var newData = [];
        data.forEach(function (dataItem) {
          var newDataItem = {};
          Object.keys(dataItem).forEach(function (key) {
            if (typeof dataItem[key] === "object") {
              newDataItem["_id"] = dataItem[key]["@id"];
              dataItem[key]["Column"].forEach(function (dataItem) {
                Object.keys(dataItem).forEach(function (key) {
                    newDataItem[dataItem[key]["@name"]] = dataItem[key]["@id"];                                    
                })
              })           
            } else {
              newDataItem[key] = dataItem[key];
            }
          });
          newData.push(newDataItem);
        });
          console.log(JSON.stringify(newData));
          chart.dataSource.data = newData
        });

      chart.data = chart.dataSource.data;

      var categoryAxis = chart.yAxes.push(new am4charts.CategoryAxis());
      categoryAxis.dataFields.category = "_id";
      categoryAxis.renderer.grid.template.location = 0;
      categoryAxis.renderer.inversed = true;


      var dateAxis = chart.xAxes.push(new am4charts.DateAxis());
      dateAxis.dateFormatter.dateFormat = "yyyy-MM-dd HH:mm";
      dateAxis.renderer.minGridDistance = 70;
      dateAxis.baseInterval = { count: 30, timeUnit: "minute" };
      dateAxis.max = new Date(2018, 0, 1, 24, 0, 0, 0).getTime();
      dateAxis.strictMinMax = true;
      dateAxis.renderer.tooltipLocation = 0;

      var series1 = chart.series.push(new am4charts.ColumnSeries());
      series1.columns.template.width = am4core.percent(80);
      series1.columns.template.tooltipText = "{name}: {openDateX} - {dateX}";

      series1.dataFields.openDateX = "fromDate";
      series1.dataFields.dateX = "toDate";
      series1.dataFields.categoryY = "name";
      series1.columns.template.propertyFields.fill = "color"; // get color from data
      series1.columns.template.propertyFields.stroke = "color";
      series1.columns.template.strokeOpacity = 1;

      chart.scrollbarX = new am4core.Scrollbar();

      chart.dataSource.events.on("error", function (ev) {
        console.log("Oopsy! Something went wrong");
      });
    })
  }
}