设置彩条上限和下限时的打印比例

Question

我有一个比例表，我正在为这些值制作一个choropleth映射，如下所示：

然后我要创建一个分别具有上限1和下限-1的颜色条。

event_y = (datetime.date.fromisoformat(start_date) + relativedelta(months = 2)).year

    cdict = {'green':  ((0.0, 0.0, 0.0),   # no red at 0
                  (0.5, 1.0, 1.0),   # all channels set to 1.0 at 0.5 to create white
                  (1.0, 0.8, 0.8)),  # set to 0.8 so its not too bright at 1

        'red': ((0.0, 0.8, 0.8),   # set to 0.8 so its not too bright at 0
                  (0.5, 1.0, 1.0),   # all channels set to 1.0 at 0.5 to create white
                  (1.0, 0.0, 0.0)),  # no green at 1

        'blue':  ((0.0, 0.0, 0.0),   # no blue at 0
                  (0.5, 1.0, 1.0),   # all channels set to 1.0 at 0.5 to create white
                  (1.0, 0.0, 0.0))   # no blue at 1
       }

# Create the colormap using the dictionary
    GnRd = colors.LinearSegmentedColormap('GnRd', cdict)

    fig, ax = plt.subplots(1, figsize=(10,10))
    ax.axis('off')
    ax.set_title(f'Change in Proportion of {race} Drivers Stopped By Service Area\n Event: {event} ({event_y})'.format(race,event,event_y), fontdict={'fontsize':'15','fontweight' : '3'})
    sm = plt.cm.ScalarMappable(cmap=GnRd, norm=plt.Normalize(vmin=-1, vmax=1,clip=True))
    fig.colorbar(sm)
    heat_diff.plot(column='prop', cmap=GnRd, linewidth=0.8, ax=ax, edgecolor='0.8')

ScalarMappable需要一个规范化参数，然后更改我正在绘制的真实值，有没有一种方法可以不进行标准化而使真实值保持不变？颜色的上限和下限分别为1和负1？

Answer 1

GeoPandas本机支持颜色条，您不必自己构建。以下应该起作用。

GnRd = colors.LinearSegmentedColormap('GnRd', cdict)

fig, ax = plt.subplots(1, figsize=(10,10))
ax.axis('off')
ax.set_title(f'Change in Proportion of {race} Drivers Stopped By Service Area\n Event: {event} ({event_y})'.format(race,event,event_y), fontdict={'fontsize':'15','fontweight' : '3'})
heat_diff.plot(column='prop', cmap=GnRd, linewidth=0.8, ax=ax,
               edgecolor='0.8', vmin=-1, vmax=1, legend=True)

我刚刚将vmin=-1, vmax=1, legend=True添加到.plot，其中前两个限制了值的范围，legend显示了色标。