'Get the zero-point if any bars are negative.'

def _ZeroPoint(self, chart):

    (min, max) = (chart.GetDependentAxis().min, chart.GetDependentAxis().max)
    out = {}
    if (min < 0):
        if (max < 0):
            out['chp'] = 1
        else:
            out['chp'] = ((- min) / float((max - min)))
    return out
