Visualising Tour De France Data In R

November 23, 2019
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drawing

The Tour de France – a short primer

The Tour de France (‘Le
Tour’) is the world’s biggest and most prestigious cycling event with a
long history spanning back as far as 1903. Each annual ‘edition’ of the
race is composed of around 21 stages that traverse the French nation,
each stage is a standalone race by itself. The racing is complex, with
each team of 9 riders competing for any combination of individual stage
wins, sprint points, mountain climbing, aggressive riding and team
ability. The most coveted prize of all is the ‘Generale Classification’
(GC) which is awarded to the rider with the lowest aggregate time at the
end of the race. Each day, the rider with the lowest aggregate time
following the previous stage wears the ‘Maillot Jaune’ (yellow jersey)
indicating that they are the current race leader.

tdf an R package for Tour de France data

The tdf package is hosted on
github and contains
information about the overall winning rider for each edition of the
race, the winner’s biographical information and the results for each
stage in each edition. To install the package, use

library(remotes)
install_github("alastairrushworth/tdf")

The package is just a container for the dataframe editions:

library(tdf)
library(tidyverse)

# visualise contents tdf::editions
glimpse(editions)
## Observations: 106
## Variables: 20
## $ edition        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, …
## $ start_date     1903-07-01, 1904-07-02, 1905-07-09, 1906-07-04, 1907-0…
## $ winner_name    "Maurice Garin", "Henri Cornet", "Louis Trousselier", "…
## $ winner_team    "La Française", "Conte", "Peugeot–Wolber", "Peugeot–Wol…
## $ distance       2428, 2428, 2994, 4637, 4488, 4497, 4498, 4734, 5343, 5…
## $ time_overall   94.55389, 96.09861, NA, NA, NA, NA, NA, NA, NA, NA, 197…
## $ time_margin    2.98916667, 2.27055556, NA, NA, NA, NA, NA, NA, NA, NA,…
## $ stage_wins     3, 1, 5, 5, 2, 5, 6, 4, 2, 3, 1, 1, 1, 4, 2, 0, 3, 4, 4…
## $ stages_led     6, 3, 10, 12, 5, 13, 13, 3, 13, 13, 8, 15, 2, 14, 14, 3…
## $ height         1.62, NA, NA, NA, NA, NA, 1.78, NA, NA, NA, NA, NA, NA,…
## $ weight         60, NA, NA, NA, NA, NA, 88, NA, NA, NA, NA, NA, NA, NA,…
## $ age            32, 19, 24, 27, 24, 25, 22, 22, 26, 23, 23, 24, 33, 30,…
## $ born           1871-03-03, 1884-08-04, 1881-06-29, 1879-06-05, 1882-1…
## $ died           1957-02-19, 1941-03-18, 1939-04-24, 1907-01-25, 1917-1…
## $ full_name      NA, NA, NA, NA, "Lucien Georges Mazan", "Lucien Georges…
## $ nickname       "The Little Chimney-sweep", "Le rigolo (The joker)", "L…
## $ birth_town     "Arvier", "Desvres", "Paris", "Moret-sur-Loing", "Pless…
## $ birth_country  "Italy", "France", "France", "France", "France", "Franc…
## $ nationality    " France", " France", " France", " France", " France", …
## $ stage_results  [[, , 

editions is a tibble whose rows each correspond to a single edition of
the Tour de France. The columns contain information about the race
itself and the overall winner, including:

  • distance is the aggregate distance in kilometres covered by the
    entire race.
  • time_overall is the time in hours taken by the winner to complete
    the race
  • time_margin is the difference in finishing times between the race
    winner and the first runner up.
  • stage_wins is the number of stages won by the eventual winner
    during the edition (note that it is possible to win the GC without
    winning any stages at all).
  • stages_led is the number of stages spent as the race leader
    (wearing the yellow jersey) by the eventual winner.
  • weight is the winner’s body weight in kilograms.
  • height is the winner’s height in meters.
  • stage_results is a column containing a list of lists. Each element
    contains a list of stage results for a particular edition of the
    Tour de France.

How has the race changed over time?

Forget ultra-marathons and tough mudder, early editions of Le Tour were
really tough. Riders were mostly self-supported, rode in woollen
jerseys for hundreds of miles per day on steel-framed bicycles. The
longest stage in Tour history was 482 kilometres (Stage 5, 1919) – the
stage winner, Jean Alavoine, took almost 19 hours to complete the stage.

*Robert Jacquinot taking a break from the 482km long Stage 5 during the
1922 Tour de France. (Image source: Wikipedia.)*

To get a sense for how the length of the race has varied since 1903, we
can visualise the total distance in the editions data:

library(ggplot2)
editions %>%
  ggplot(aes(x = start_date, y = distance, 
             color = edition)) +
  geom_point() + 
  xlab('Race start date') + 
  ylab('Distance in kilometres') + 
  ggtitle('Tour de France total distance covered over time') + 
  theme(legend.position = "none")

It’s pretty clear that over time, the distances covered have decreased
dramatically, and have roughly stabilised at about 3500 kilometres
during the last 2 decades (still a huge distance). You can see that the
longest ever Tour de France edition was in 1926, with a total distance
covered of 5,745 kilometres!

On the face of it, it seems like the riders of today have it
substantially easier compared to riders of the past. But how fast are
today’s riders going?

library(ggrepel)
editions %>%
  ggplot(aes(x = start_date, y = distance / time_overall, 
             color = edition)) +
  geom_point(na.rm = TRUE) + 
  geom_label_repel(data = editions %>% sample_n(20), 
                  aes(label = winner_name), size = 2.3,  
                  nudge_y = -9, na.rm = TRUE,
                  segment.alpha = 0.2) + 
  xlab('Edition start date') + 
  ylab('Average speed km/h') + 
  ggtitle('Tour de France winners average speed') + 
  theme(legend.position = "none")

They’re going pretty fast. It looks like while the race has been getting
gradually shorter, the speeds have been getting much faster. The change
also coincides with professionalisation of the sport, better equipment
and smarter training so it’s hard to provide an exact account for the
change in speed. It’s worth highlighting the top two fastest average
speeds in Tour de France history:

# Top 5 average speeds of Tour de France winners
editions %>%
  mutate(speed = distance / time_overall) %>%
  select(start_date, winner_name, speed) %>%
  arrange(desc(speed)) %>%
  print(n = 2)
## # A tibble: 106 x 3
##   start_date winner_name     speed
##                   
## 1 1998-07-11 Marco Pantani    41.7
## 2 2005-07-02 Lance Armstrong  41.7
## # … with 104 more rows

The two fastest ever editions of the Tour de France were won by Marco
Pantani (in 1998) and Lance Armstrong (in 2005), both of whom were later
stripped of these (and other) wins for their use of banned
performance-enhancing substances. The speed of doped riders in such Tour
editions was so obviously faster than non-doped riders, that French
media declared a culture of “Cyclisme a deux vitesses” (“two-speed
cycling”
). It is unknown how much riders still use banned substances
for performance enhancement, but the average speeds of the Pantani /
Armstrong years have not been reached in any edition since.

Note: the the data in the tdf package retains the winning times of
banned, disqualified and otherwise sanctioned riders for the purposes of
data analysis. The overall standings are as they would have appeared on
the final day of the race – therefore please note that the officially
recognised winner of a particular edition may not be the rider with the
fastest time.

How have the riders changed over time?

France is a mountainous country, and a crucial ingredient for success in
the Tour de France is a rider’s ability to climb hills quickly and
efficiently. Hill climbing is a fight against gravity that pits a
rider’s strength against their total weight (bike + equipment + body).
The rider has two options to improve: get stronger and get leaner. Using
the editions data we can explore the latter over time by using rider
height and weight data to calculate body mass index (BMI), which is
a (very rough) proxy for leanness.

drawing

library(ggrepel)
editions %>%
  ggplot(aes(x = start_date, y = weight / height^2, 
             color = edition)) +
  geom_point(na.rm = TRUE) + 
  geom_label_repel(data = editions %>% sample_n(20), 
                  aes(label = winner_name), size = 1.8,  
                  nudge_y = 4, na.rm = TRUE,
                  segment.alpha = 0.2) + 
  xlab('Edition start date') + 
  ylab('Body mass index') + 
  ggtitle('Tour de France winners body mass index') + 
  theme(legend.position = "none")

It’s pretty clear that over time, the trend has been towards winners
having lower BMI, and likely being leaner overall. Apart from the
obvious issues with BMI as a metric (body shapes are more complex than
just height and weight) it’s interesting to consider why this trend has
occurred. It’s tempting to conclude that more careful dieting and
preparation in recent years has lead to riders having lower body fat
percentages, which can enhance a rider’s power to weight ratio and
overall performance. However, it could also be due to changes in the
race: if race winning becomes more dependent on performance in the
mountains (for example, because the number of mountain stages has
increased overall) this could result in the lighter and leaner athletes
tending to excel overall.

Stage results

The column stage_results contains the breakdown of results by stage
for each edition of the Tour de France. For example, the results of the
final stage of the 2019 Tour de France can be printed using

editions$stage_results$`2019`$`stage-21`
## # A tibble: 155 x 8
##     rank time     rider         bib_number   age team            points elapsed 
##                                   
##  1     1 3H 4M 8S Ewan Caleb           161    25 Lotto Soudal       100 3H 4M 8S
##  2     2 0S       Groenewegen …         84    26 Team Jumbo-Vis…     70 3H 4M 8S
##  3     3 0S       Bonifazio Ni…        172    25 Team Total Dir…     50 3H 4M 8S
##  4     4 0S       Richeze Maxi…         27    36 Deceuninck - Q…     40 3H 4M 8S
##  5     5 0S       Boasson Hage…        201    32 Team Dimension…     32 3H 4M 8S
##  6     6 0S       Greipel André        215    37 Team Arkéa Sam…     26 3H 4M 8S
##  7     7 0S       Trentin Matt…        107    29 Mitchelton-Sco…     22 3H 4M 8S
##  8     8 0S       Stuyven Jasp…        138    27 Trek - Segafre…     18 3H 4M 8S
##  9     9 0S       Arndt Nikias         142    27 Team Sunweb         14 3H 4M 8S
## 10    10 0S       Sagan Peter           11    29 BORA - hansgro…     10 3H 4M 8S
## # … with 145 more rows

The important columns for the stage data are

  • time the finishing time of the stage winner and time difference to
    the winner.
  • rider the rider name formatted as ‘Surname Forename’.
  • age age of the rider at the start of the stage.
  • elapsed the time taken to reach the finish line – this is stored
    as a lubridate::period object for easier printing and
    manipulation.

In the case above, Caleb Ewan won the finish line sprint of the final
stage. Since the first 53 riders were part of a contiguous group of
riders, they were granted the same finishing time as Ewan, but their
finishing order corresponds to the order they passed the finish line.

*Caleb Ewan wins the sprint on stage 21 of the 2019 Tour de France.
(Image source: AFP/Getty Images)*

Comments? Suggestions? Issues?

Any feedback is welcome! Find me on twitter at
rushworth_a or write a github
issue
.

To leave a comment for the author, please follow the link and comment on their blog: Alastair Rushworth.

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