Timeline bar using matplotlib & PolyCollection - Python

Question

I have been trying to replicate @theimportanceofbeingernest 's answer to Timeline bar graph using python and matplotlib and can't seem to get the correct output graph.

Here is my current output

Here is my desired output (but with using my data etc.)

I'm struggling to identify the issue. Any help will be greatly appreciated! Thank you.

Here's the code:

import datetime as dt
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
from matplotlib.collections import PolyCollection

data = [(dt.datetime(1900, 1, 1, 14, 19, 26), dt.datetime(1900, 1, 1, 14, 19, 29), 'index'),
        (dt.datetime(1900, 1, 1, 14, 19, 29), dt.datetime(1900, 1, 1, 14, 19, 31), 'links'),
        (dt.datetime(1900, 1, 1, 14, 19, 31), dt.datetime(1900, 1, 1, 14, 19, 33), 'guides'),
        (dt.datetime(1900, 1, 1, 14, 19, 33), dt.datetime(1900, 1, 1, 14, 19, 35), 'prices'),
        (dt.datetime(1900, 1, 1, 14, 19, 35), dt.datetime(1900, 1, 1, 16, 39, 47), 'index'),
        (dt.datetime(1900, 1, 1, 16, 39, 47), dt.datetime(1900, 1, 1, 16, 39, 48), 'prices')]

cats = {'index': 1, 'links': 2, 'guides': 3, 'prices': 4}
colormapping  = {'index': 'C0', 'links': 'C1', 'guides': 'C2', 'prices': 'C3'} 

verts = []
colors = []
for d in data:
    v =  [(mdates.date2num(d[0]), cats[d[2]]-.4),
          (mdates.date2num(d[0]), cats[d[2]]+.4),
          (mdates.date2num(d[1]), cats[d[2]]+.4),
          (mdates.date2num(d[1]), cats[d[2]]-.4),
          (mdates.date2num(d[0]), cats[d[2]]-.4)]
    verts.append(v)
    colors.append(colormapping[d[2]])

bars = PolyCollection(verts, facecolors=colors)

fig, ax = plt.subplots()
ax.add_collection(bars)
ax.autoscale()
loc = mdates.MinuteLocator(byminute=[0,30])
ax.xaxis.set_major_locator(loc)
ax.xaxis.set_major_formatter(mdates.AutoDateFormatter(loc))

ax.set_yticks([1,2,3,4])
ax.set_yticklabels(['index', 'links', 'guides', 'prices'])
plt.show()

JohanC · Accepted Answer · 2020-04-04 10:28:54Z

1

Your time differences are extremely short. They are a few seconds, while yourthe x-range is a few hours. So, these bars basically get invisible.

Note that in matplotlib areas are usually drawn without antialiasing, which is useful when putting together multiple semitransparent areas. Lines, however, are drawn with some thickness (in screenspace) and antialiased. Therefore, setting an explicit edgecolor helps to visualize these "bars".

bars = PolyCollection(verts, facecolors=colors, edgecolors=colors)

edited Apr 4, 2020 at 10:28

answered Apr 3, 2020 at 22:42

JohanC

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1 Comment

Johno Cown Over a year ago

of course! Thank you for your help - this has fixed my issue! Hope you have a good day sir :)

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