'Calculate the percentage drop related to the "worst"
drawdown seen.'

def calculate_max_drawdown_pct(self):

    drawdown_series = pd.Series(self.drawdowns)
    equity_series = pd.Series(self.equity)
    bottom_index = drawdown_series.idxmax()
    try:
        top_index = equity_series[:bottom_index].idxmax()
        pct = (((equity_series.ix[top_index] - equity_series.ix[bottom_index]) / equity_series.ix[top_index]) * 100)
        return round(pct, 4)
    except ValueError:
        return np.nan
