def METHOD_NAME(x,y, t=None):
    """ creates a quad tree from a list of x,y positions"""
    di = max(x.max() - x.min(), y.max() - y.min())
    qt = qtRoot(100*floor(x.min()/100), 100*ceil((x.min()+di)/100),100*floor(y.min()/100), 100*ceil((y.min()+di)/100))
    if t is None:
        for xi, yi in zip(x,y):
            qt.insert(qtRec(xi,yi, None))
    else:
        for xi, yi, ti in zip(x,y, t):
            qt.insert(qtRec(xi,yi, ti))
    return qt