def bot_yformatter(self, val, type=''):
        """custom formatter for FuncFormatter() and bottom panel"""
        fmt = '%1.5g'

        ax = self.panel_bot.axes.yaxis

        ticks = ax.get_major_locator()()
        dtick = ticks[1] - ticks[0]

        if   dtick > 29999:
            fmt = '%1.5g'
        elif dtick > 1.99:
            fmt = '%1.0f'
        elif dtick > 0.099:
            fmt = '%1.1f'
        elif dtick > 0.0099:
            fmt = '%1.2f'
        elif dtick > 0.00099:
            fmt = '%1.3f'
        elif dtick > 0.000099:
            fmt = '%1.4f'
        elif dtick > 0.0000099:
            fmt = '%1.5f'

        s =  fmt % val
        s.strip()
        s = s.replace('+', '')
        while s.find('e0')>0:
            s = s.replace('e0','e')
        while s.find('-0')>0:
            s = s.replace('-0','-')
        return s