Add volunteer frequency histogram code.

files/cli.py

@@ -5,6 +5,7 @@ from files.__main__ import app
 from files.commands.cron import cron_app_worker
 from files.commands.seed_db import seed_db
 from files.commands.volunteer_janitor_recalc import volunteer_janitor_recalc
+from files.commands.volunteer_janitor_histogram import volunteer_janitor_histogram_cmd
 from files.commands.cron_setup import cron_setup
 import files.classes
 

files/commands/volunteer_janitor_histogram.py

@@ -0,0 +1,35 @@
+
+import pprint
+
+from files.classes.volunteer_janitor import VolunteerJanitorRecord
+
+from files.__main__ import app, db_session
+
+@app.cli.command('volunteer_janitor_histogram')
+def volunteer_janitor_histogram_cmd():
+    import pandas as pd
+    import matplotlib.pyplot as plt
+
+    result_set = db_session().query(VolunteerJanitorRecord.recorded_utc).all()
+
+    # convert the result into a pandas DataFrame
+    df = pd.DataFrame(result_set, columns=['recorded_utc'])
+
+    # convert the date column to datetime
+    df['recorded_utc'] = pd.to_datetime(df['recorded_utc'])
+
+    # set 'recorded_utc' as the index of the DataFrame
+    df.set_index('recorded_utc', inplace=True)
+
+    # resample the data to daily frequency
+    df_resampled = df.resample('D').size()
+
+    # plot the resampled DataFrame
+    df_resampled.plot(kind='line')
+    plt.title('Density of Dates over Time')
+    plt.xlabel('Date')
+    plt.ylabel('Count')
+    
+    # save the figure in SVG format
+    plt.savefig('output.svg', format='svg')
+    print(len(result_set))