How to mark some of checkbox list value as checked in Angular?

I have a checkbox list with websites. This list is created from 10 values, and I need to mark first 5 elements as checked. How we can do this in Angular? I use Angular Material checkbox.

 <section >
          <p>Value:</p>
          <p *ngFor="let data of websites | async">
            <mat-checkbox [value]="data.name">{{data.name}}</mat-checkbox>
          </p>
</section>

“websites” from *ngForm is an observable in which I get all websites.