- series
a factor denoting UK series (1-10).
- episode
a factor denoting episode number within a series.
- uk_airdate
a date denoting original airdate of episode in the UK.
- viewers_7day
number of viewers in millions within a 7-day window
from airdate.
- viewers_28day
number of viewers in millions within a 28-day window
from airdate.
- network_rank
an integer denoting the episode's weekly ranking within
network (note that the networks changed for series 8 and later).
- channels_rank
an integer denoting the episode's weekly ranking
across all channels.
- bbc_iplayer_requests
number of BBC iPlayer requests (note: not
available for all series, and only for series that aired on the BBC).
- episode_count
continuous episode count.