matplotlib · shadidsh · Mar 9, 2018 · Mar 12, 2018 · Mar 14, 2018 · Mar 14, 2018
diff --git a/doc/api/next_api_changes/2018-03-15-SS.rst b/doc/api/next_api_changes/2018-03-15-SS.rst
@@ -0,0 +1,5 @@
+``AutoDateLocator.get_locator`` now contains reduced datetime overlaps
+````````````````````````````````````````````````````````````````````````
+
+Due to issue #7712, the interval frequency of datetime ticks gets reduced due to 
+avoid overlapping tick labels.
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -1208,12 +1208,20 @@ def __init__(self, tz=None, minticks=5, maxticks=None,
         The interval is used to specify multiples that are appropriate for
         the frequency of ticking. For instance, every 7 days is sensible
         for daily ticks, but for minutes/seconds, 15 or 30 make sense.
-        You can customize this dictionary by doing::
+        You can customize this dictionary by doing:
 
           locator = AutoDateLocator()
           locator.intervald[HOURLY] = [3] # only show every 3 hours
+
+        In order to avoid overlapping dates, another dictionary was
+        created to map date intervals to the format of the date used in
+        rcParams. In addition, the figsize and font is used from the axis,
+        and a new setting in rcparams['autodatelocator.spacing'] is added
+        and used to let the user decide when spacing should be used. This
+        was done because rotation at this point in runtime is not known.
         """
         DateLocator.__init__(self, tz)
+
         self._locator = YearLocator()
         self._freq = YEARLY
         self._freqs = [YEARLY, MONTHLY, DAILY, HOURLY, MINUTELY,
@@ -1242,6 +1250,16 @@ def __init__(self, tz=None, minticks=5, maxticks=None,
             MICROSECONDLY: [1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000,
                             5000, 10000, 20000, 50000, 100000, 200000, 500000,
                             1000000]}
+
+        self.eachtick = {
+                    YEARLY: rcParams['date.autoformatter.year'],
+                    MONTHLY: rcParams['date.autoformatter.month'],
+                    DAILY: rcParams['date.autoformatter.day'],
+                    HOURLY: rcParams['date.autoformatter.hour'],
+                    MINUTELY: rcParams['date.autoformatter.minute'],
+                    SECONDLY: rcParams['date.autoformatter.second'],
+                    MICROSECONDLY: rcParams['date.autoformatter.microsecond']}
+
         self._byranges = [None, range(1, 13), range(1, 32),
                           range(0, 24), range(0, 60), range(0, 60), None]
 
@@ -1314,11 +1332,34 @@ def get_locator(self, dmin, dmax):
         #  bysecond, unused (for microseconds)]
         byranges = [None, 1, 1, 0, 0, 0, None]
 
+        # Required attributes to get width from figure's normal points
+        axis_name = getattr(self.axis, 'axis_name', '')
+        axes = getattr(self.axis, 'axes', None)
+        label = getattr(self.axis, 'label', None)
+        figure = getattr(self.axis, 'figure', None)
+        transfig = getattr(figure, 'transFigure', None)
+        maxwid = rcParams['figure.figsize'][0]
+
+        # estimated font ratio on font size 10
+        if label is not None:
+            font_ratio = label.get_fontsize() / 10
+        else:
+            font_ratio = rcParams['font.size'] / 10
+
+        # a ratio of 8 date characters per inch is 'estimated'
+        if (axes is not None and transfig is not None):
+            bbox = axes.get_position(original=False)
+            figwidth = transfig.transform(bbox.get_points())[1][0]
+            dpi = figure.get_dpi()
+            maxwid = (figwidth / dpi) * 8
+
+        spacing = (rcParams["autodatelocator.spacing"] == "generous")
+
         # Loop over all the frequencies and try to find one that gives at
         # least a minticks tick positions.  Once this is found, look for
         # an interval from an list specific to that frequency that gives no
         # more than maxticks tick positions. Also, set up some ranges
-        # (bymonth, etc.) as appropriate to be passed to rrulewrapper.
+        # (bymonth, etc.) as appropriate to be passed to rrulewrapper
         for i, (freq, num) in enumerate(zip(self._freqs, nums)):
             # If this particular frequency doesn't give enough ticks, continue
             if num < self.minticks:
@@ -1328,11 +1369,24 @@ def get_locator(self, dmin, dmax):
                 byranges[i] = None
                 continue
 
+            # Compute at runtime the size of date label with given format
+            if (axis_name == 'x'):
+                datelen_ratio = \
+                    len(dmin.strftime(self.eachtick[freq])) * font_ratio
+            else:
+                datelen_ratio = 1 * font_ratio
+
             # Find the first available interval that doesn't give too many
             # ticks
             for interval in self.intervald[freq]:
-                if num <= interval * (self.maxticks[freq] - 1):
-                    break
+
+                # Using an estmation of characters per inch, reduce
+                # intervals untill we get no overlaps
+                apply_spread = (not spacing or
+                                ((num/interval) * datelen_ratio) <= maxwid)
+                if (num <= interval * (self.maxticks[freq] - 1)):
+                    if (apply_spread):
+                        break
             else:
                 # We went through the whole loop without breaking, default to
                 # the last interval in the list and raise a warning
@@ -1344,7 +1398,6 @@ def get_locator(self, dmin, dmax):
 
             # Set some parameters as appropriate
             self._freq = freq
-
             if self._byranges[i] and self.interval_multiples:
                 byranges[i] = self._byranges[i][::interval]
                 interval = 1

diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -1213,6 +1213,9 @@ def _validate_linestyle(ls):
     'date.autoformatter.second': ['%H:%M:%S', validate_string],
     'date.autoformatter.microsecond': ['%M:%S.%f', validate_string],
 
+    # To avoid overlapping date invervals, we can set the spacing in advance
+    # 'generous' is set to avoid overlapping, otherwise 'tight' by default
+    'autodatelocator.spacing' : ['tight', validate_string],
     #legend properties
     'legend.fancybox': [True, validate_bool],
     'legend.loc': ['best', validate_legend_loc],

diff --git a/lib/matplotlib/tests/baseline_images/test_dates/datetime_daily_overlap.png b/lib/matplotlib/tests/baseline_images/test_dates/datetime_daily_overlap.png
diff --git a/lib/matplotlib/tests/baseline_images/test_dates/datetime_hourly_overlap.png b/lib/matplotlib/tests/baseline_images/test_dates/datetime_hourly_overlap.png
diff --git a/lib/matplotlib/tests/baseline_images/test_dates/datetime_minutely_overlap.png b/lib/matplotlib/tests/baseline_images/test_dates/datetime_minutely_overlap.png
diff --git a/lib/matplotlib/tests/baseline_images/test_dates/datetime_monthly_overlap.png b/lib/matplotlib/tests/baseline_images/test_dates/datetime_monthly_overlap.png
diff --git a/lib/matplotlib/tests/test_dates.py b/lib/matplotlib/tests/test_dates.py
@@ -10,6 +10,7 @@
 from matplotlib.testing.decorators import image_comparison
 import matplotlib.pyplot as plt
 import matplotlib.dates as mdates
+from matplotlib import rcParams
 
 
 def test_date_numpyx():
@@ -405,12 +406,12 @@ def _create_auto_date_locator(date1, date2):
                  '2180-01-01 00:00:00+00:00', '2200-01-01 00:00:00+00:00']
                 ],
                [datetime.timedelta(weeks=52),
-                ['1997-01-01 00:00:00+00:00', '1997-02-01 00:00:00+00:00',
-                 '1997-03-01 00:00:00+00:00', '1997-04-01 00:00:00+00:00',
-                 '1997-05-01 00:00:00+00:00', '1997-06-01 00:00:00+00:00',
-                 '1997-07-01 00:00:00+00:00', '1997-08-01 00:00:00+00:00',
-                 '1997-09-01 00:00:00+00:00', '1997-10-01 00:00:00+00:00',
-                 '1997-11-01 00:00:00+00:00', '1997-12-01 00:00:00+00:00']
+               ['1997-01-01 00:00:00+00:00', '1997-02-01 00:00:00+00:00',
+                '1997-03-01 00:00:00+00:00', '1997-04-01 00:00:00+00:00',
+                '1997-05-01 00:00:00+00:00', '1997-06-01 00:00:00+00:00',
+                '1997-07-01 00:00:00+00:00', '1997-08-01 00:00:00+00:00',
+                '1997-09-01 00:00:00+00:00', '1997-10-01 00:00:00+00:00',
+                '1997-11-01 00:00:00+00:00', '1997-12-01 00:00:00+00:00']
                 ],
                [datetime.timedelta(days=141),
                 ['1997-01-01 00:00:00+00:00', '1997-01-22 00:00:00+00:00',
@@ -453,7 +454,6 @@ def _create_auto_date_locator(date1, date2):
                  '1997-01-01 00:00:00.001500+00:00']
                 ],
                )
-
     for t_delta, expected in results:
         d2 = d1 + t_delta
         locator = _create_auto_date_locator(d1, d2)
@@ -612,3 +612,47 @@ def test_tz_utc():
 def test_num2timedelta(x, tdelta):
     dt = mdates.num2timedelta(x)
     assert dt == tdelta
+
+
+@image_comparison(baseline_images=['datetime_daily_overlap'],
+                  extensions=['png'])
+def test_datetime_daily_overlap():
+    # issue 7712 for overlapping daily dates
+    plt.rcParams['date.autoformatter.day'] = "%Y-%m-%d"
+    plt.rcParams["autodatelocator.spacing"] = "generous"
+    dates = [datetime.datetime(2018, 1, i) for i in range(1, 30)]
+    values = list(range(1, 30))
+    plt.plot(dates, values)
+
+
+@image_comparison(baseline_images=['datetime_monthly_overlap'],
+                  extensions=['png'])
+def test_datetime_monthly_overlap():
+    # issue 7712 for overlapping monthly dates
+    plt.rcParams['date.autoformatter.month'] = '%Y-%m'
+    plt.rcParams["autodatelocator.spacing"] = "generous"
+    dates = [datetime.datetime(2018, i, 1) for i in range(1, 11)]
+    values = list(range(1, 11))
+    plt.plot(dates, values)
+
+
+@image_comparison(baseline_images=['datetime_hourly_overlap'],
+                  extensions=['png'])
+def test_datetime_hourly_overlap():
+    # issue 7712 for overlapping hourly dates
+    plt.rcParams['date.autoformatter.hour'] = '%m-%d %H'
+    plt.rcParams["autodatelocator.spacing"] = "generous"
+    dates = [datetime.datetime(2018, 1, 1, i) for i in range(1, 20)]
+    values = list(range(1, 20))
+    plt.plot(dates, values)
+
+
+@image_comparison(baseline_images=['datetime_minutely_overlap'],
+                  extensions=['png'])
+def test_datetime_minutely_overlap():
+    # issue 7712 for overlapping date ticks in minutely intervals
+    plt.rcParams['date.autoformatter.minute'] = '%d %H:%M'
+    plt.rcParams["autodatelocator.spacing"] = "generous"
+    dates = [datetime.datetime(2018, 1, 1, 1, i) for i in range(1, 55)]
+    values = list(range(1, 55))
+    plt.plot(dates, values)
diff --git a/matplotlibrc.template b/matplotlibrc.template
@@ -352,6 +352,8 @@ backend      : $TEMPLATE_BACKEND
 #date.autoformatter.second   : %H:%M:%S
 #date.autoformatter.microsecond   : %M:%S.%f
 
+#autodatelocator.spacing : tight ## if generous, add extra spacing to avoid overlap, otherwise tight
+
 #### TICKS
 ## see http://matplotlib.org/api/axis_api.html#matplotlib.axis.Tick
 #xtick.top            : False  ## draw ticks on the top side