added index date formatter example

jdh2358 · jdh2358 · commit 8c3f33ef1d4d · 2007-06-11T20:57:42.000Z
svn path=/trunk/matplotlib/; revision=3385
diff --git a/examples/date_index_formatter.py b/examples/date_index_formatter.py
@@ -0,0 +1,37 @@
+
+"""
+When plotting daily data, a frequent request is to plot the data
+ignoring skips, eg no extra spaces for weekends.  This is particularly
+common in financial time series, when you may have data for M-F and
+not Sat, Sun and you don't want gaps in the x axis.  The approach is
+to simply use the integer index for the xdata and a custom tick
+Formatter to get the appropriate date string for a given index.
+"""
+
+import numpy
+from matplotlib.mlab import csv2rec
+from pylab import figure, show
+from matplotlib.dates import Formatter
+
+r = csv2rec('data/msft.csv')[-40:]
+
+class MyFormatter(Formatter):
+    def __init__(self, dates, fmt='%Y-%m-%d'):
+        self.dates = dates
+        self.fmt = fmt
+
+    def __call__(self, x, pos=0):
+        'Return the label for time x at position pos'
+        ind = int(round(x))
+        if ind>=len(self.dates) or ind<0: return ''
+
+        return self.dates[ind].strftime(self.fmt)
+
+formatter = MyFormatter(r.date)
+
+fig = figure()
+ax = fig.add_subplot(111)
+ax.xaxis.set_major_formatter(formatter)
+ax.plot(numpy.arange(len(r)), r.close, 'o-')
+fig.autofmt_xdate()
+show()
diff --git a/examples/pick_event_demo2.py b/examples/pick_event_demo2.py
@@ -24,6 +24,7 @@ def onpick(event):
     N = len(event.ind)
     if not N: return True
 
+
     figi = figure()
     for subplotnum, dataind in enumerate(event.ind):
         ax = figi.add_subplot(N,1,subplotnum+1)
