I found the gtag() function worked, instead of the ga() function.
In the index.html file, within the <head> section:
<script async src="https://www.googletagmanager.com/gtag/js?id=TrackingId"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'TrackingId');
</script>
In the AngularJS code:
app.run(function ($rootScope, $location) {
$rootScope.$on('$routeChangeSuccess', function() {
gtag('config', 'TrackingId', {'page_path': $location.path()});
});
});
Replace TrackingId with your own Tracking Id.