title: Angular how to set radio button checked in Reactive Form
body: <p>I am building a very simple form like this:</p>
  <pre><code>  form = new FormGroup({
      choose: new FormControl('', Validators.required)
    })
  </code></pre>
  <p>I know that I can set my radio button to checked like this:</p>
  <pre><code>  form = new FormGroup({
      choose: new FormControl('1', Validators.required)
    })
  </code></pre>
  <p>My question is how to set radio button later. Maybe in ngOnInit()? Background is that I first do some API calls in init and after this I want to choose which radio button should be checked and which not. I don't want to do it in Template. Or is this only way?</p>