如何定义Python Bokeh RangeSlider.on_change回调函数来更改绘图的IndexFilter

Question

我正在尝试为RangeSlider实现一个python回调函数。"滑块值"(Slider Value(应指示IndexFilter应获取哪个索引进行显示。

例如：如果rangeslider.value为(3,25(，我的绘图应该只包含/查看索引为3到25的数据。

from bokeh.io import output_file, show
from bokeh.models import ColumnDataSource, GMapOptions, CustomJS, CDSView, IndexFilter
from bokeh.plotting import gmap, ColumnDataSource, figure
from bokeh.layouts import column, row
from bokeh.models.widgets import RangeSlider 
import numpy as np
def slider_callback(attr, old, new):
p.view = CDSView(source=source, filters=[IndexFilter(np.arange(new.value[0], new.value[1]))])
v.view = CDSView(source=source, filters=[IndexFilter(np.arange(new.value[0], new.value[1]))])

# data set
lon = [[48.7886, 48.7887, 48.7888, 48.7889, 48.789], 
[48.7876, 48.7877, 48.78878, 48.7879, 48.787], 
[48.7866, 48.7867, 48.7868, 48.7869, 48.786],
[48.7856, 48.7857, 48.7858, 48.7859, 48.785],
[48.7846, 48.7847, 48.7848, 48.7849, 48.784]]
lat = [[8.92, 8.921, 8.922, 8.923, 8.924],
[8.91, 8.911, 8.912, 8.913, 8.914],
[8.90, 8.901, 8.902, 8.903, 8.904],
[8.89, 8.891, 8.892, 8.893, 8.894],
[8.88, 8.881, 8.882, 8.883, 8.884]]
time = [0, 1, 2, 3, 4, 5]
velocity = [23, 24, 25, 24, 20]
lenght_dataset = len(lon)

# define source and map
source = ColumnDataSource(data = {'x': lon, 'y': lat, 't': time, 'v': velocity})
view = CDSView(source=source, filters=[IndexFilter(np.arange(0, lenght_dataset))])
map_options = GMapOptions(lat=48.7886, lng=8.92, map_type="satellite", zoom=13)
p = gmap("MY_API_KEY", map_options, title="Trajectory Map")
v = figure(plot_width=400, plot_height=400, title="Velocity")

# plot lines on map
p.multi_line('y', 'x', view=view, source=source, line_width=1)
v.line('t', 'v', view=view, source=source, line_width=3)

# slider to limit plotted data
range_slider = RangeSlider(title="Data Range Slider: ", start=0, end=lenght_dataset, value=(0, lenght_dataset), step=1) 
range_slider.on_change('value', slider_callback)

# Layout to plot and output
layout = row(column(p, range_slider),
column(v)
)
output_file("diag_plot_bike_data.html")
show(layout)

Answer 1

一些注意事项：

• time比其他列长-你会收到一个警告。在下面的代码中，我刚刚删除了它的最后一个元素
• 带有过滤器的view通常不应用于像线条这样的连续字形(特别是v.line-multi_line很好(。你会收到关于它的警告。但是如果IndexFilter中的索引总是连续的，那么你应该没事。无论哪种方式，都可以使用线段图示符来避免警告
• 在回调中，您试图在地物上设置视图-视图仅存在于字形渲染器上
• 通常，您不希望重新创建视图，而是希望重新创建尽可能少的Bokeh模型。理想情况下，您只需要更改过滤器的indices字段。但是Bokeh中缺少一些连线，因此您必须设置视图的filters字段，如下所示
• Python回调的new参数接收作为第一个参数传递给相应on_change调用的属性的新值。在这种情况下，它将是一个元组，因此应该使用new[0]而不是new.value[0]
• 由于您已经决定使用Python回调，因此您不能再使用show并拥有一个静态HTML文件——您将不得不使用curdoc().add_root和bokeh serve。UI需要Python代码在运行时的某个地方运行
• 当更改滑块值时，您会注意到multi_line的单独段将连接在一起——这是一个错误，我刚刚创建https://github.com/bokeh/bokeh/issues/10589为了它

下面是一个工作示例：

from bokeh.io import curdoc
from bokeh.layouts import column, row
from bokeh.models import GMapOptions, CDSView, IndexFilter
from bokeh.models.widgets import RangeSlider
from bokeh.plotting import gmap, ColumnDataSource, figure
lon = [[48.7886, 48.7887, 48.7888, 48.7889, 48.789],
[48.7876, 48.7877, 48.78878, 48.7879, 48.787],
[48.7866, 48.7867, 48.7868, 48.7869, 48.786],
[48.7856, 48.7857, 48.7858, 48.7859, 48.785],
[48.7846, 48.7847, 48.7848, 48.7849, 48.784]]
lat = [[8.92, 8.921, 8.922, 8.923, 8.924],
[8.91, 8.911, 8.912, 8.913, 8.914],
[8.90, 8.901, 8.902, 8.903, 8.904],
[8.89, 8.891, 8.892, 8.893, 8.894],
[8.88, 8.881, 8.882, 8.883, 8.884]]
time = [0, 1, 2, 3, 4]
velocity = [23, 24, 25, 24, 20]
lenght_dataset = len(lon)
# define source and map
source = ColumnDataSource(data={'x': lon, 'y': lat, 't': time, 'v': velocity})
view = CDSView(source=source, filters=[IndexFilter(list(range(lenght_dataset)))])
map_options = GMapOptions(lat=48.7886, lng=8.92, map_type="satellite", zoom=13)
p = gmap("API_KEY", map_options, title="Trajectory Map")
v = figure(plot_width=400, plot_height=400, title="Velocity")
p.multi_line('y', 'x', view=view, source=source, line_width=1)
v.line('t', 'v', view=view, source=source, line_width=3)
range_slider = RangeSlider(title="Data Range Slider: ", start=0, end=lenght_dataset, value=(0, lenght_dataset), step=1)

def slider_callback(attr, old, new):
view.filters = [IndexFilter(list(range(*new)))]

range_slider.on_change('value', slider_callback)
layout = row(column(p, range_slider), column(v))
curdoc().add_root(layout)