angular - Angular2 Trigger form.valueChanges manually -

i'm subscribing form changes with:

this.form.valuechanges.subscribe(formdata => { // data saved here. });

when click button in form changes 1 of input values. somehow valuechanges subscribe not being triggered. can manually?

i believe need map valuechanges before subscribing like:

 this.physicalform.valuechanges        .map((value) => {           return value;        })        .subscribe((value) => {          this.selectedphysical.activitylevel = this.physicalform.value.activitylevel;        });