matplotlib/examples/api/date_index_formatter.py at master · codemaru/matplotlib · GitHub

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"""

When plotting time series, e.g., financial time series, one often wants

to leave out days on which there is no data, eh weekends. The example

below shows how to use an 'index formatter' to achieve the desired plot

"""

from __future__ import print_function

import numpy as np

import matplotlib.pyplot as plt

import matplotlib.mlab as mlab

import matplotlib.cbook as cbook

import matplotlib.ticker as ticker

datafile = cbook.get_sample_data('aapl.csv', asfileobj=False)

print('loading %s' % datafile)

r = mlab.csv2rec(datafile)

r.sort()

r = r[-30:] # get the last 30 days

# first we'll do it the default way, with gaps on weekends

fig, ax = plt.subplots()

ax.plot(r.date, r.adj_close, 'o-')

fig.autofmt_xdate()

# next we'll write a custom formatter

N = len(r)

ind = np.arange(N) # the evenly spaced plot indices

def format_date(x, pos=None):

thisind = np.clip(int(x + 0.5), 0, N - 1)

return r.date[thisind].strftime('%Y-%m-%d')

fig, ax = plt.subplots()

ax.plot(ind, r.adj_close, 'o-')

ax.xaxis.set_major_formatter(ticker.FuncFormatter(format_date))

fig.autofmt_xdate()

plt.show()