title: How to set default values in ng-select in angular6?
body: <p>I am using angular6 <code>multi-select</code> which have a list of items coming in an array of objects from angular service on <code>ngOnInit</code> like this which is passing into <code>multi-select</code> :</p>
  
  <pre><code>this.sensorTypes = [
    { label : "Power", value : "P"},
    { label : "Current", value : "C"},
    { label : "Voltage", value : "V"}
  ]
  </code></pre>
  
  <p>I want to set 2 values by default in <code>multi-select</code> when form will load. For this i am binding <code>ngModel</code> on <code>multi-select</code>and in that variable i am setting values on <code>ngOnInit</code> like this </p>
  
  <pre><code>this.selectedAttributes = [
    {label : "Current", value : "C"},
    {label : "Voltage", value : "V"}
  ]
  </code></pre>
  
  <p>In my component.html i am creating <code>multi-select</code> like this : </p>
  
  <pre><code>&lt;div class="form-group row"&gt;
    &lt;div class="col-sm-10"&gt;
      &lt;ng-select 
         [ngClass]="'ng-select'" 
         [(ngModel)]="selectedAttributes" 
         [ngModelOptions]="{standalone: true}" 
         [options]="sensorTypes"
         [multiple]="true"&gt;
      &lt;/ng-select&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>But values are not setting by default in multi-select.</p>