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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
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Johno Cown
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1 Answers1

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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)

resulting plot

JohanC
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