Altair：使用绑定时选择所有值

Question

第一次呈现图表时，binding_select()已选择none/all，因此显示所有值。使用下拉列表进行选择后，如何再次选择所有值

在下面的示例中，首先显示所有数据点。然后进行选择，仅显示与该位置对应的数据点。然后如何返回到图表中显示所有数据点的原始状态

source = pd.DataFrame({'Position':['Center','Center','Power Forward','Point Guard','Point Guard','Shooting Guard','Power Forward','Point Guard','Point Guard'],
                      'Points_Per_Game':[12 , 13, 15 , 21, 22, 9, 8, 5, 7],
                      'Games_Played':[22, 9, 8, 5, 7 , 12 , 13, 15 , 21]})

position_dropdown = alt.binding_select(options=list(source.Position.unique()))
position_selection = alt.selection_single(fields=['Position'], bind=position_dropdown, name='Player ')

alt.Chart(source).mark_circle(size=100).encode(
    x='Games_Played:N',
    y='Points_Per_Game:N',

).properties(selection=interval).add_selection(
    position_selection,
).transform_filter(
    position_selection
)

Answer 1

您需要在下拉选择中包含选项None，以便在未选择任何内容时调用默认行为。您可以设置一个显示“全部”的标签，以便清楚该选项的作用：

source = pd.DataFrame({'Position':['Center','Center','Power Forward','Point Guard','Point Guard','Shooting Guard','Power Forward','Point Guard','Point Guard'],
                      'Points_Per_Game':[12 , 13, 15 , 21, 22, 9, 8, 5, 7],
                      'Games_Played':[22, 9, 8, 5, 7 , 12 , 13, 15 , 21]})

position_dropdown = alt.binding_select(
    options=[None] + list(source.Position.unique()), labels = ['All'] + list(source.Position.unique()))
position_selection = alt.selection_single(fields=['Position'], bind=position_dropdown, name='Player ')

alt.Chart(source).mark_circle(size=100).encode(
    x='Games_Played:N',
    y='Points_Per_Game:N',
).add_selection(
    position_selection,
).transform_filter(
    position_selection
)