rotate date-labels of plot; show ticks for days and 6-hour intervals

src/langfingaz/plotMeetings.py

@@ -1,11 +1,15 @@
 from pathlib import Path
 from typing import List
-import matplotlib.pyplot as pyplot
+from datetime import date
+
+import matplotlib.pyplot as plt
+import matplotlib.dates as mdates
 
 from langfingaz import loadData
 from langfingaz import parseMeetings
 from langfingaz.parseMeetings import BbbStatus, Meeting
 from langfingaz.util import fileUtil
+from langfingaz.util import util
 
 
 def getDefaultPlotFolder() -> Path:
@@ -40,25 +44,49 @@ def doPlotMeetings(bbbStati: List[BbbStatus]) -> Path:
         videos.append(bbbStatus.videoCount)
         voices.append(bbbStatus.voiceParticipantCount)
 
-    # Note that even in the OO-style, we use `.pyplot.figure` to create the figure.
+    _a, _b = plt.subplots()  # Create a figure and an axes.
-    _a, _b = pyplot.subplots()  # Create a figure and an axes.
+    fig: plt.Figure = _a
-    fig: pyplot.Figure = _a
     ax = _b  # of type plt.axes.Axes ??
-    if not (issubclass(type(fig), pyplot.Figure)):
+    if not (issubclass(type(fig), plt.Figure)):
         raise ValueError("expected Figure")
 
-    ax.plot(time, participants, label='participants')  # Plot some data on the axes.
+    ax.plot(time, participants, label='participants')
-    ax.plot(time, videos, label='video')  # Plot more data on the axes...
+    ax.plot(time, videos, label='video')
-    ax.plot(time, voices, label='voice')  # ... and some more.
+    ax.plot(time, voices, label='voice')
+
+    # format the ticks (on x-axis)
+    days = mdates.DayLocator()
+    hours = mdates.HourLocator(interval=6)  # every 6 hours one minor tick
+    dateFmt = mdates.DateFormatter('%Y-%m-%d')
+
+    ax.xaxis.set_major_locator(days)
+    ax.xaxis.set_major_formatter(dateFmt)
+    ax.xaxis.set_minor_locator(hours)
+
+    # round to nearest day
+    dateMin = time[0].date()  # round floor
+    dateMax = util.roundCeilingByDay(time[-1])  # round ceiling
+    ax.set_xlim(dateMin, dateMax)
+
     ax.set_xlabel('time')  # Add an x-label to the axes.
     ax.set_ylabel('numbers')  # Add a y-label to the axes.
     ax.set_title("BigBlueButton Statistics")  # Add a title to the axes.
     ax.legend()  # Add a legend.
 
+    # rotates and right aligns the x labels (dates), and moves the bottom of the
+    # axes up to make room for them
+    # https://matplotlib.org/api/_as_gen/matplotlib.figure.Figure.html#matplotlib.figure.Figure.autofmt_xdate
+    fig.autofmt_xdate()
+
+    imgFormat = 'png'
     image: Path = getDefaultPlotFolder().joinpath(
-        "{}_until_{}".format(fileUtil.asString(time[0]), fileUtil.asString(time[-1]))
+        "{}_until_{}.{}".format(
+            fileUtil.asString(time[0]),
+            fileUtil.asString(time[-1]),
+            imgFormat
         )
-    fig.savefig(image)
+    )
+    fig.savefig(image, format=imgFormat)
     # plt.show()
 
     return image

src/langfingaz/util/util.py

@@ -1,4 +1,5 @@
 import time
+import datetime
 
 
 def sleep(seconds: float):
@@ -13,6 +14,49 @@ def indentMultilineStr(s: str, indentWith='\t'):
     return indented
 
 
+# def roundFloorByDay(t) -> datetime.date:
+#     """
+#     rounds the (date)time up to the closest full day before or equal this point of time
+#     (round floor)
+#
+#     :param t: datetime.date or datetime.datetime
+#     :return: the closest full day before or equal to (date)time t
+#     """
+#
+#     # note: order of datetime and date type check matters
+#     #  as datetime is a SUBCLASS of date
+#     if issubclass(type(t), datetime.datetime):
+#         return t.date()
+#     elif issubclass(type(t), datetime.date):
+#         return t
+#     else:
+#         raise ValueError("illegal argument")
+
+
+def roundCeilingByDay(t) -> datetime.date:
+    """
+    rounds the (date)time up to the closest full day after or equal to this point of time
+    (round ceiling)
+
+    :param t: datetime.date or datetime.datetime
+    :return: the closest full day after or equal to (date)time t
+    """
+
+    # note: order of datetime and date type check matters
+    #  as datetime is a SUBCLASS of date
+    if issubclass(type(t), datetime.datetime):
+        t: datetime.datetime  # "cast" to datetime.datetime for IDE linting
+
+        if t.minute == 0 and t.second == 0 and t.microsecond == 0:
+            return t.date()
+        else:
+            return datetime.date(year=t.year, month=t.month, day=t.day + 1)
+    elif issubclass(type(t), datetime.date):
+        return t
+    else:
+        raise ValueError("illegal argument")
+
+
 def asString(o: object):
     attrs = vars(o)  # attributes and their values
     return '\n'.join("%s: %s" % item for item in attrs.items())