当 x 轴在日期时间时用散景绘制光线

Question

Trying to draw a vertical ray at an important date in my dataset to highlight trends before/after that date. I understand how to draw the ray with an x-axis that isn't in datetimes, but I've been struggling with getting it to work when x is in datetime. Here's what I tried:

from bokeh.plotting import figure, output_file, show
from datetime import datetime as dt
from math import pi

p = figure(title = 'stuff',
           x_axis = 'date',
           y_axis = datapoints,
           x_axis_type = "datetime",
           tools='pan, wheel_zoom, box_zoom, reset, resize, previewsave',
           plot_width=1000)
#dates and data are lists containing datetime objects and y values
p.line(dates, data, line_width=1)
p.xaxis.major_label_orientation = pi/4
p.ray(x = dt(year, month, day), y = 0, length = 0, angle_units = "deg", 
      angle = 90, color = 'black')
output_file('data.html')
show(p)

This yields a long stacktrace, with the following error:

ValueError: expected an element of either String, Dict(String, Either(String, Instance(Transform), Instance(ColorMapper), Float)) or Float, got datetime.datetime(2014, 9, 18, 0, 0)

Is this simply not supported when x axis is in datetimes, or have I missed something in documentation?

Answer 1

Figured it out. I originally passed in a list of datetime objects for my x axis. I replaced that list with a list of timestamps in milliseconds, then got the corresponding timestamp in milliseconds for the call-out date and used that to define the ray. Revised code:

p.line(lst_of_epoch_times_ms, data, line_width=1)
p.xaxis.major_label_orientation = pi/4
p.ray(x = ms_timestamp_callout, y = 0, length = 0, angle_units = "deg",
      angle = 90, color = 'black')

Hope this helps anyone who stumbles on this question.

Answer 2

使用此处指示的 Span

Span annotations are lines that are orthogonal to the x or y axis of a plot. They have a single dimension (width or height) and go from one edge of the plot area to the opposite edge.