python matplot of events each minute

Question

I am trying to use matplot to graph the number of events in a specific minute generated by different inputs.

broadly similar to the screen clip below, but showing a simple 24 hour period only.

Part of my problem is that I don't know how to work with Y axis data that is not a complete set. eg, if all I have is 2 events, one at 04:04 (y=5) and one at 13:22 (y=1) how do I make that show on a graph for the full 24 hour period please?

I have been experimenting with stacked histtype=step, but I am not making any progress and can't find any examples in http://matplotlib.org/gallery.html

If there is a better plotter for this sort of output I would be happy to try that too.

Thanks

Edit: Adding example that is not quite what I want. need it to: (1). use time on the x axis (2). use time for the events (3). bars to start at 0 (4). not have that line in the middle (5). later on add different events in a different colour

import matplotlib
# Force matplotlib to not use any Xwindows backend.
matplotlib.use('Agg')
import matplotlib.pyplot as plt

a = [1,2,5,6,9,11,15,17,18]
plt.hlines(1,0,24)  # Draw a horizontal line
plt.eventplot(a, orientation='horizontal', colors='b')

plt.savefig('foo.png', bbox_inches='tight')

I'm not sure what you mean exactly, but, perhaps, set_xlim() (to set the 24-hour window) will help? Some simplified runnable example would be helpful. — fjarri
– fjarri, Commented Dec 16, 2015 at 1:39
Are you looking for event plots? matplotlib.org/examples/pylab_examples/eventplot_demo.html — tacaswell
– tacaswell, Commented Dec 16, 2015 at 5:28
Thanks very much for your comments. I am a complete noob to Python and matplot so I am still struggling. The eventplot_demo top left pane looks as if it might be very helpful but I can't work out how to code a more simple example so I can start to learn. I will keep trying & post a solution if I manage it. — Mike Hinson
– Mike Hinson, Commented Dec 16, 2015 at 13:03

Brian Huey · Accepted Answer · 2015-12-16 17:43:26Z

1

I think you want to set a 24 hour period in minutes using plt.xlim which creates an index from 0-1440 along the xaxis. Then you can append bars with height equal to your y value, and located based on the index.

plt.figure(figsize=(29, 9))
hours = 24
mins = 60
xlabels = ['%02d:%02d' % (divmod(i, 60)) for i in range(0, mins * hours, 10)]
plt.xlim(0, hours * mins)
plt.ylim(0,6)
xdata_org = ['04:04', '13:22']
ydata = [5, 1]
def get_min(time):
    l = time.split(':')
    return int(l[0]) * 60 + int(l[1])
xdata = [get_min(i) for i in xdata_org]
plt.bar(xdata, ydata, width=1)
plt.xticks(range(0, hours * mins, 10), xlabels, rotation='vertical', fontsize=9)
plt.subplots_adjust(left=0.05, right=0.95, bottom=0.3)

answered Dec 16, 2015 at 17:43

Brian Huey

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1 Comment

Mike Hinson Over a year ago

Thanks Brian Huey, this is exactly what I was attempting. It is surprisingly complex. I was expecting matplot to have more native time handing. That is why I couldn't find it in the documentation I think. Thanks again.

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