How to mat-button-toggle by default selected in angular

I fixed it. Simply add the value attribute to the mat-button-toggle-group tag.

<mat-button-toggle-group #group="matButtonToggleGroup" value="All">
<mat-button-toggle value="Heritage">
    <span>Heritage</span>
</mat-button-toggle>
<mat-button-toggle value="Nature">
    <span>Nature</span>
</mat-button-toggle>
<mat-button-toggle value="People">
    <span>People</span>
</mat-button-toggle>
<mat-button-toggle value="All">
    <span>All</span>
</mat-button-toggle>