DOC: add example and whats new

jklymak · jklymak · commit 8d3014d292d0 · 2018-07-04T14:01:49.000-07:00
diff --git a/doc/users/next_whats_new/concise_date_formatter.rst b/doc/users/next_whats_new/concise_date_formatter.rst
@@ -0,0 +1,37 @@
+New date formatter: `~.dates.ConciseDateFormatter`
+--------------------------------------------------
+
+The automatic date formatter used by default can be quite verbose.  A new
+formatter can be accessed that tries to make the tick labels appropriately
+concise.
+
+  .. plot::
+
+    import matplotlib.pyplot as plt
+    import matplotlib.dates as mdates
+    import numpy as np
+
+    # make a timeseries...
+    dt = np.timedelta64(2, 'h', dtype='datetime64[s]')
+    dates = np.arange('2005-02', '2005-04', dt, dtype='datetime64[s]')
+    N = len(dates)
+
+    np.random.seed(19680801)
+    y = np.cumsum(np.random.randn(N))
+
+    lims = [(np.datetime64('2005-02'), np.datetime64('2005-04')),
+            (np.datetime64('2005-02-03'), np.datetime64('2005-02-15')),
+            (np.datetime64('2005-02-03 11:00'), np.datetime64('2005-02-04 13:20'))]
+    fig, axs = plt.subplots(3, 1, constrained_layout=True)
+    for nn, ax in enumerate(axs):
+        # activate the formatter here.
+        locator = mdates.AutoDateLocator()
+        formatter = mdates.ConciseDateFormatter(locator)
+        ax.xaxis.set_major_locator(locator)
+        ax.xaxis.set_major_formatter(formatter)
+
+        ax.plot(dates, y)
+        ax.set_xlim(lims[nn])
+    axs[0].set_title('Concise Date Formatter')
+
+    plt.show()
diff --git a/examples/ticks_and_spines/date_concise_formatter.py b/examples/ticks_and_spines/date_concise_formatter.py
@@ -0,0 +1,54 @@
+"""
+================================================
+Formatting date ticks using ConciseDateFormatter
+================================================
+
+Finding good tick values and formatting the ticks for an axis that
+has date data is often a challenge.  `~.dates.ConciseDateFormatter` is
+meant to improve the strings chosen at various date intervals.
+
+"""
+import datetime
+import matplotlib.pyplot as plt
+import matplotlib.dates as mdates
+import numpy as np
+
+# make a timeseries...
+dt = np.timedelta64(2, 'h', dtype='datetime64[s]')
+dates = np.arange('2005-02', '2005-04', dt, dtype='datetime64[s]')
+N = len(dates)
+
+np.random.seed(19680801)
+y = np.cumsum(np.random.randn(N))
+
+fig, axs = plt.subplots(3, 1, constrained_layout=True)
+lims = [(np.datetime64('2005-02'), np.datetime64('2005-04')),
+        (np.datetime64('2005-02-03'), np.datetime64('2005-02-15')),
+        (np.datetime64('2005-02-03 11:00'), np.datetime64('2005-02-04 13:20'))]
+for nn, ax in enumerate(axs):
+    ax.plot(dates, y)
+    ax.set_xlim(lims[nn])
+    # rotate_labels...
+    for label in ax.get_xticklabels():
+        label.set_rotation(40)
+        label.set_horizontalalignment('right')
+axs[0].set_title('Default Date Formatter')
+plt.show()
+
+#############################################################################
+# The default date formater is a bit verbose, but Matplotlib has an
+# an alternative that can be chosen with a few extra lines of code.  Note,
+# for this size axes the labels do not need to be rotated.
+
+fig, axs = plt.subplots(3, 1, constrained_layout=True)
+for nn, ax in enumerate(axs):
+    locator = mdates.AutoDateLocator()
+    formatter = mdates.ConciseDateFormatter(locator)
+    ax.xaxis.set_major_locator(locator)
+    ax.xaxis.set_major_formatter(formatter)
+
+    ax.plot(dates, y)
+    ax.set_xlim(lims[nn])
+axs[0].set_title('Concise Date Formatter')
+
+plt.show()
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -762,13 +762,14 @@ def __call__(self, x, pos=0):
         return num2date(self.t[ind], self.tz).strftime(self.fmt)
 
 
-class NewDateFormatter(ticker.Formatter):
+class ConciseDateFormatter(ticker.Formatter):
     """
-    This class attempts to figure out the best format to use.  This is
+    This class attempts to figure out the best format to use for the
+    date, and to make it as compact as possible, but still complete. This is
     most useful when used with the :class:`AutoDateLocator`.
 
     >>> locator = AutoDateLocator()
-    >>> formatter = NewDateFormatter(locator)
+    >>> formatter = ConciseDateFormatter(locator)
 
     """
 
@@ -1525,7 +1526,7 @@ def get_locator(self, dmin, dmax):
             self._freq = freq
 
             if self._byranges[i] and self.interval_multiples:
-                if i == DAILY and interval == 14:
+                if i <= DAILY and interval == 14:
                     # just make first and 15th.  Avoids 30th.
                     byranges[i] = [1, 15]
                 else:
