With a new actor being announced tomorrow, it got me pondering about the good Doctor. Specifically, who is the longest serving doctor? IMDB has the data:

whos <- data.frame(
  doctor = c(
    "William Hartnell",
    "Patrick Troughton",
    "Jon Pertwee",
    "Tom Baker",
    "Peter Davison",
    "Colin Baker",
    "Sylvester McCoy",
    "Paul McGann",
    "Christopher Ecclestone",
    "David Tennant",
    "Matt Smith"
  ),
  n_episodes = c(
    136,
    127,
    129,
    173,
    70,
    35,
    42,
    1,
    13,
    49,
    44
  ),
  stringsAsFactors = FALSE
)
whos$doctor <- factor(whos$doctor, levels = whos$doctor)

Let’s plot it to see how it changes over time.

library(ggplot2)
(bars <- ggplot(whos, aes(doctor, n_episodes)) +
  geom_bar(stat = "identity") +
  coord_flip()
) 

There was a definite shift after Tom Baker towards a shorter term as the doctor. In terms of screen time, the shift is a little less pronounced due to the move from 25 minutes to 45 minutes per episode from Christopher Ecclestone onwards (and for one of the Colin Baker series).