matplotlib · jklymak · Jan 5, 2022 · Dec 6, 2021 · Dec 6, 2021 · jklymak
diff --git a/examples/lines_bars_and_markers/scatter_demo2.py b/examples/lines_bars_and_markers/scatter_demo2.py
@@ -9,9 +9,10 @@
 import matplotlib.pyplot as plt
 import matplotlib.cbook as cbook
 
-# Load a numpy record array from yahoo csv data with fields date, open, close,
-# volume, adj_close from the mpl-data/example directory. The record array
-# stores the date as an np.datetime64 with a day unit ('D') in the date column.
+# Load a numpy record array from yahoo csv data with fields date, open, high,
+# low, close, volume, adj_close from the mpl-data/sample_data directory. The
+# record array stores the date as an np.datetime64 with a day unit ('D') in
+# the date column.
 price_data = (cbook.get_sample_data('goog.npz', np_load=True)['price_data']
               .view(np.recarray))
 price_data = price_data[-250:]  # get the most recent 250 trading days

diff --git a/examples/text_labels_and_annotations/date.py b/examples/text_labels_and_annotations/date.py
@@ -26,10 +26,10 @@
 import matplotlib.dates as mdates
 import matplotlib.cbook as cbook
 
-# Load a numpy structured array from yahoo csv data with fields date, open,
-# close, volume, adj_close from the mpl-data/example directory.  This array
-# stores the date as an np.datetime64 with a day unit ('D') in the 'date'
-# column.
+# Load a numpy record array from yahoo csv data with fields date, open, high,
+# low, close, volume, adj_close from the mpl-data/sample_data directory. The
+# record array stores the date as an np.datetime64 with a day unit ('D') in
+# the date column.
 data = cbook.get_sample_data('goog.npz', np_load=True)['price_data']
 
 fig, axs = plt.subplots(3, 1, figsize=(6.4, 7), constrained_layout=True)

diff --git a/examples/text_labels_and_annotations/date_index_formatter.py b/examples/text_labels_and_annotations/date_index_formatter.py
diff --git a/examples/ticks/date_index_formatter.py b/examples/ticks/date_index_formatter.py
@@ -0,0 +1,83 @@
+"""
+=====================================
+Custom tick formatter for time series
+=====================================
+
+.. redirect-from:: /gallery/text_labels_and_annotations/date_index_formatter
+.. redirect-from:: /gallery/ticks/date_index_formatter2
+
+When plotting daily data, e.g., financial time series, one often wants
+to leave out days on which there is no data, for instance weekends, so that
+the data are plotted at regular intervals without extra spaces for the days
+with no data.
+The example shows how to use an 'index formatter' to achieve the desired plot.
+"""
+
+import numpy as np
+import matplotlib.pyplot as plt
+import matplotlib.cbook as cbook
+import matplotlib.lines as ml
+from matplotlib.dates import DateFormatter, DayLocator
+from matplotlib.ticker import Formatter
+
+
+# Load a numpy record array from yahoo csv data with fields date, open, high,
+# low, close, volume, adj_close from the mpl-data/sample_data directory. The
+# record array stores the date as an np.datetime64 with a day unit ('D') in
+# the date column (``r.date``).
+r = (cbook.get_sample_data('goog.npz', np_load=True)['price_data']
+     .view(np.recarray))
+r = r[:9]  # get the first 9 days
+
+fig, (ax1, ax2) = plt.subplots(nrows=2, figsize=(6, 6),
+                               constrained_layout={'hspace': .15})
+
+# First we'll do it the default way, with gaps on weekends
+ax1.plot(r.date, r.adj_close, 'o-')
+
+# Highlight gaps in daily data
+gaps = np.flatnonzero(np.diff(r.date) > np.timedelta64(1, 'D'))
+for gap in r[['date', 'adj_close']][np.stack((gaps, gaps + 1)).T]:
+    ax1.plot(gap.date, gap.adj_close, 'w--', lw=2)
+ax1.legend(handles=[ml.Line2D([], [], ls='--', label='Gaps in daily data')])
+
+ax1.set_title("Plot y at x Coordinates")
+ax1.xaxis.set_major_locator(DayLocator())
+ax1.xaxis.set_major_formatter(DateFormatter('%a'))
+
+
+# Next we'll write a custom index formatter. Below we will plot
+# the data against an index that goes from 0, 1,  ... len(data).  Instead of
+# formatting the tick marks as integers, we format as times.
+def format_date(x, _):
+    try:
+        # convert datetime64 to datetime, and use datetime's strftime:
+        return r.date[round(x)].item().strftime('%a')
+    except IndexError:
+        pass
+
+# Create an index plot (x defaults to range(len(y)) if omitted)
+ax2.plot(r.adj_close, 'o-')
-# Create an index plot (x defaults to range(len(y)) if omitted)
-ax2.plot(r.adj_close, 'o-')
+# Create an index plot:
+ax2.plot(np.arange(0, len(r.adj_close)), r.adj_close, 'o-')
-# Create an index plot (x defaults to range(len(y)) if omitted)
-ax2.plot(r.adj_close, 'o-')
+# Create an index plot:
+ax2.plot(np.arange(0, len(r.adj_close)), r.adj_close, 'o-')
+
+ax2.set_title("Plot y at Index Coordinates Using Custom Formatter")
+ax2.xaxis.set_major_formatter(format_date)  # internally creates FuncFormatter
+
+#############################################################################
+# Instead of passing a function into `.Axis.set_major_formatter` you can use
+# any other callable, e.g. an instance of a class that implements __call__:
+
+
+class MyFormatter(Formatter):
+    def __init__(self, dates, fmt='%a'):
+        self.dates = dates
+        self.fmt = fmt
+
+    def __call__(self, x, pos=0):
+        """Return the label for time x at position pos."""
+        try:
+            return self.dates[round(x)].item().strftime(self.fmt)
+        except IndexError:
+            pass
+
+
+ax2.xaxis.set_major_formatter(MyFormatter(r.date, '%a'))
diff --git a/examples/ticks/date_index_formatter2.py b/examples/ticks/date_index_formatter2.py