title: how to make mat radio button selected by default by displaying a key and sending value associated with the key
body: <p>I have some radio buttons. I want to select one option by default. I have read somewhere that [checked] should work.
  I have made the data structure like that but it is not working.</p>
  
  <pre><code>  &lt;mat-radio-group class="example-radio-group" [(ngModel)]="favoriteSeason" &gt;
    &lt;mat-radio-button class="exmple-radio-button" *ngFor="let season of seasons" [value]="season.value" [checked]="season.checked"&gt;
      {{season.key}}-{{season.checked}}
    &lt;/mat-radio-button&gt;
  &lt;/mat-radio-group&gt;
  &lt;div class="example-selected-value"&gt;Your favorite season is: {{favoriteSeason}}&lt;/div&gt;
  </code></pre>
  
  <p>ts</p>
  
  <pre><code>  export class RadioNgModelExample {
        favoriteSeason = '';
        seasons = [
          {
      key: 'Winter',
      checked: false,
      value: 1
          },
             {
      key: 'Spring',
      checked: true,
       value: 2
          },{
          key: 'Summer',
      checked: false,
       value: 3  
          },{
            key: 'Autumn',
      checked: false,
       value: 4      
          }];
      }
  </code></pre>
  
  <p><a href="https://stackblitz.com/edit/angular-drf2s5-55tcr1?file=app/radio-ng-model-example.ts" rel="nofollow noreferrer">stackblitz</a></p>