title: Convert "String" value to a number
body: <p>I would like to populate a Google maps with markers.</p>
  
  <p>The marker coordinates I get as String:</p>
  
  <pre><code>"marker": {
        "latitude": "52.31976",
        "longitude": "7.00454"
  }
  </code></pre>
  
  <p>My service for retrieving the JSON:</p>
  
  <pre><code>   /**
       * Get All Sources
      */
      getSources(): Observable&lt;Source.RootObject[]&gt; {
          return this._http.get(this._sourceUrl)
              .map((response: Response) =&gt; &lt;Source.RootObject[]&gt;response.json());
      }
  </code></pre>
  
  <p>My component handling the call:</p>
  
  <pre><code>   /**
       * Set local _sources array equal data from stream
       * @param _sourceService
       * @param router
       */
      constructor(
          private _sourceService: SourceService,
          private router: Router
      ) {
          this._sourceService.getSources()
              .subscribe(_sources =&gt; this.createSources(_sources));
      }
  </code></pre>
  
  <p>The createMArkers method:</p>
  
  <pre><code> /**
       * Bad workaround for markers
       */
      private createSources(result): void {
          this._sources = result;
  
          let sourceLat: number, sourceLng: number;
          this.positions = [];
          let latlong = null;
  
          for (let i = 0; i &lt; this._sources.length; i++) {
  
              sourceLat = +this._sources[i].marker.latitude;
              sourceLng = +this._sources[i].marker.longitude;
              //  Create position object
              latlong = { lat: sourceLat, lng: sourceLng };
  
              this.positions.push([this._sources[i].id, latlong]);
          }
      }
  </code></pre>
  
  <p>The HTML markup with Angular:</p>
  
  <pre><code>&lt;ngui-map zoom="8" center="{{center}}" &gt;
  
      &lt;marker *ngFor="let pos of positions"
                [icon]="{
                 url: 'assets/icons/marker.svg',
                 anchor: [16,16],
                 size: [32,32],
                 scaledSize: [32,32]
               }"
              (click)="printLog(pos)"
              [position]="pos.latlong"&gt;&lt;/marker&gt;
    &lt;/ngui-map&gt;
  </code></pre>
  
  <p>I would not like to create a seperate array for the positions but just use the array of source objects (e.g. source.marker.longitude)</p>
  
  <p>What I tried:</p>
  
  <ul>
  <li><code>[position]="marker.latitude, marker.longitude"</code> is not accepted because it is a string value.</li>
  <li><code>[position]=marker.latitude, marker.longitude</code> with the hope it will be cast.</li>
  <li><code>[position]={{marker}}</code></li>
  </ul>
  
  <p>Thanks in advance.</p>