SF.net SVN: matplotlib: [5436] trunk/matplotlib/examples/api/ date_index_formatter.py

[<jd...@us...>]

Revision: 5436
          http://matplotlib.svn.sourceforge.net/matplotlib/?rev=5436&view=rev
Author:   jdh2358
Date:     2008-06-09 10:47:32 -0700 (Mon, 09 Jun 2008)

Log Message:
-----------
added date index formatter example

Added Paths:
-----------
    trunk/matplotlib/examples/api/date_index_formatter.py

Added: trunk/matplotlib/examples/api/date_index_formatter.py
===================================================================
--- trunk/matplotlib/examples/api/date_index_formatter.py	                        (rev 0)
+++ trunk/matplotlib/examples/api/date_index_formatter.py	2008-06-09 17:47:32 UTC (rev 5436)
@@ -0,0 +1,36 @@
+"""
+When plotting time series, eg 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
+"""
+import numpy as np
+import matplotlib.pyplot as plt
+import matplotlib.mlab as mlab
+import matplotlib.ticker as ticker
+
+r = mlab.csv2rec('../data/aapl.csv')
+r.sort()
+r = r[-30:]  # get the last 30 days
+
+
+# first we'll do it the default way, with gaps on weekends
+fig = plt.figure()
+ax = fig.add_subplot(111)
+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 = plt.figure()
+ax = fig.add_subplot(111)
+ax.plot(ind, r.adj_close, 'o-')
+ax.xaxis.set_major_formatter(ticker.FuncFormatter(format_date))
+fig.autofmt_xdate()
+
+plt.show()


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