Added a floor to z-score algorithm, and a cron file

conf/solr_cron

@@ -0,0 +1,7 @@
+PATH=/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+
+
+#Updating Solr's trending scores.
+0 * * * *  su openlibrary "python scripts/calculate_trending_scores_hourly.py"
+
+5 0 * * * su openlibrary "python scripts/calculate_trending_scores_daily.py"

scripts/calculate_trending_scores_daily.py

@@ -42,11 +42,10 @@ def form_inplace_updates(work_id: str, current_day: int, new_value: int):
             load_config(ol_config)
     current_day = datetime.datetime.now().weekday()
     work_data = fetch_works(current_day)
-    print(work_data)
+
     request_body = [
         form_inplace_updates(work_id, current_day, work_data[work_id])
         for work_id in work_data
     ]
-    print(request_body)
+
     resp = get_solr().update_in_place(request_body)
-    print(resp)

scripts/calculate_trending_scores_hourly.py

@@ -63,8 +63,18 @@ def fetch_works(current_hour: int):
     return doc_data
 
 
+# If the arithmetic mean is below 10/7 (i.e: there have been)
+# less than 10 reading log events for the work in the past week,
+# it should not show up on trending.
+AVERAGE_DAILY_EVENTS_FLOOR = 10 / 7
+
+
+# This function calculates how many standard deviations the value for the last
+# 24 hours is away from the mean.
 def get_z_score(solr_doc: dict, count: int, current_hour: int):
     arith_mean = sum([solr_doc[f'trending_score_daily_{i}'] for i in range(7)]) / 7
+    if arith_mean < ():
+        return 0
     last_24_hours_value = (
         solr_doc['trending_score_hourly_sum']
         + count