Redrawing UIButton using CGRectMake doesn't update UIButton position?

I'm trying to update the position and size of several UIButtons in my app by using:

-(void)viewDidAppear:(BOOL)animated {
    _UIButton1.frame = CGRectMake(-7, 35, 212, 77);
    _UIButton2.frame = CGRectMake(139, 149, 290, 77);
    // And so on for several more buttons
}

However, when I use this code, these buttons just appear at wherever the location is set on the Storyboard, not where I'm setting it programmatically. How would I make these buttons appear at a location this is different than the one I have set in my Storyboard?