META
I've updated the groupings in the task description's Research Questions section based on the feedback @MGerlach shared offline.

Weekly update:

• generated first dataset of readers of English Wikipedia on a single day capturing for each actor: i) the number of pageloads to articles in the main namespace; ii) the number of days since the last access; iii) how many other namespaces (beyond main namespace) were visited.
• will start exploratory analysis of the data in the next week(s)

weekly update:

• started first exploratory analysis of a 1% sample of reading sessions from a single day (~438k sessions)
• percentage of reading sessions with single or multiple pageviews:

• percentage of reading sessions with last-access: 1 day, 1 week (but more than 1 day), 1 month (but more than 1 week), non-returning:

• percentage of reading sessions only accessing main namespace or also accessing pages in any other namespace:

• next step: look at combination of different facets

answering questions 1./2.:

• we separate all readers into two subgroups i) people who visit a single Wikipedia page and ii) people who visit multiple Wikipedia pages on a single day.
• for each group separately, we calculate what percentage:
  • Did not visit Wikipedia before (non-recurring)
  • Visited Wikipedia within in the last month (7<d<=31)
  • Visited Wikipedia within in the last week (1<d<=7)
  • Visited Wikipedia yesterday (d=1)

Summary: For readers who visit multiple Wikipedia pages we find that a substantially larger fraction visited the previous day (40% vs 25% in comparison to readers who visit only a single Wikipedia article on a given day)

answering questions 3. (how do above distributions change when considering the reader visited articles beyond the main namespace).

• First, the fraction of readers visiting articles beyond the main namespace ("ns>0") is much smaller than those visiting only articles in the main namespace ("ns=0"): It is roughly around 1%

• Second, the small group of readers who visit articles beyond the main namespace ("ns>0"), is much more likely have visited multiple articles in the main namespace as well. In fact, the ratio between single and multiple pageviews is inverted: i) for the majority of readers (those that visit only the main namespace "ns=0") around 2/3 visit a single article and 1/3 visit multiple articles; ii) in contrast, for the non-main namespace readers, around 1/3 visit a single article and 2/3 visit multiple articles (in the main namespace).

• Third, we find that the regularity of the visit changes only slightly when considering readers who visit only the main namespace ("ns=0") or also visit other namespaces ("ns>0"). Two main observations: i) the readers who visit other namespaces and visit multiple pages ("ns>0 / multi") have the highest fraction of readers whose previous visit was on the previous day ("d=1"); around 45%. ii) However, this is only slightly higher compared to readers who only visit the main namespace but visited multiple articles ("ns=0 / multi"); thus, the main distinguishing feature is between readers who visit only a single article ("ns=0 / single" and "ns>0 / single") and those who visit multiple articles in the main namespace ("ns=0 / multi" and "ns>0 / multi")