def draw_vector(v0, v1, ax=None, **kwargs):
    """
    Plots an arrow represnting the direction and magnitue of a principal
    component on a biaxial plot.

    Modified after Jake VanderPlas' Python Data Science Handbook
    https://jakevdp.github.io/PythonDataScienceHandbook/     05.09-principal-component-analysis.html

    Todo
    -----
        Update for ternary plots.

    """
    ax = ax
    arrowprops = dict(arrowstyle='->', linewidth=2, shrinkA=0, shrinkB=0)
    arrowprops.update(kwargs)
    ax.annotate('', v1, v0, arrowprops=arrowprops)
