Angular 8: Automatically check checkbox when a condition is matched

I'm working in a side panel filter for my page, I have the parent checkbox (Select all) and the children checkboxes(specific filters).

Here is what I want, if I select a children I want the parent checkbox to be partially checked, see image below:

link to example image

Currently this is my code, my parent checkbox ngModel is set to "dataSource.data.length == selectedAssetTypeFilters.length"

<mat-panel-title>

<mat-checkbox [(ngModel)]="dataSource.data.length == selectedAssetTypeFilters.length" (click)="$event.stopPropagation()" (keydown)="$event.stopPropagation()" (change)="onSelectAll($event, 'assettype')" title="Select All">Data Asset Type</mat-checkbox> </mat-panel-title> </mat-expansion-panel-header>

<div class="filter-content">

<mat-tree [dataSource]="dataSource" [treeControl]="treeControl" class="example-tree">

<!-- This is the tree node template for leaf nodes -->

<mat-tree-node *matTreeNodeDef="let node" matTreeNodeToggle>

<li class="mat-tree-node">

<mat-checkbox [(ngModel)]="node.checked" (change)="onFilterUpdate(node, 'assettype');" title="">

How can I do this?