'Add radio buttons to :class:`matplotlib.axes.Axes` instance *ax*
*labels*
A len(buttons) list of labels as strings
*active*
The index into labels for the button that is active
*activecolor*
The color of the button when clicked'

def __init__(self, ax, labels, active=0, activecolor=u'blue'):

    AxesWidget.__init__(self, ax)
    self.activecolor = activecolor
    self.value_selected = None
    ax.set_xticks([])
    ax.set_yticks([])
    ax.set_navigate(False)
    dy = (1.0 / (len(labels) + 1))
    ys = np.linspace((1 - dy), dy, len(labels))
    cnt = 0
    axcolor = ax.get_facecolor()
    self.labels = []
    self.circles = []
    for (y, label) in zip(ys, labels):
        t = ax.text(0.25, y, label, transform=ax.transAxes, horizontalalignment=u'left', verticalalignment=u'center')
        if (cnt == active):
            self.value_selected = label
            facecolor = activecolor
        else:
            facecolor = axcolor
        p = Circle(xy=(0.15, y), radius=0.05, edgecolor=u'black', facecolor=facecolor, transform=ax.transAxes)
        self.labels.append(t)
        self.circles.append(p)
        ax.add_patch(p)
        cnt += 1
    self.connect_event(u'button_press_event', self._clicked)
    self.cnt = 0
    self.observers = {}
