The grammar of graphics

Lecture 2

Dr. Benjamin Soltoff

Cornell University
INFO 5001 - Fall 2024

August 29, 2024

Announcements

Application exercises 00 are ungraded
If you cannot access RStudio Workbench yet, let me know
Lab on Friday
No class on Tuesday

Warm up

Examining data visualization

Discuss the following for the visualization.

What is the visualization trying to show?
What is effective, i.e. what is done well?
What is ineffective, i.e. what could be improved?
What are you curious about after looking at the visualization?

03:00

Application exercise

The Bechdel test

A measurement of representation of women in film

In order to pass the test, a movie must have:

At least two named women in it
Who talk to each other
About something besides a man

The Bechdel test

`ae-00`

ae-00-bechdel

Go to ae-00-bechdel and clone the repo in RStudio.
Open and render the Quarto document ae-00-bechdel-viz.qmd, review the document, and fill in the blanks.

Warning

ae-00-bechdel is hosted on GitHub.com because we have not configured your authentication method for Cornell’s GitHub. We will do this tomorrow in lab.

Recap of AE

Construct plots with ggplot().
Components of ggplots are separated by +s.
The formula is (almost) always as follows:

ggplot(DATA, aes(x = X - VAR, y = Y - VAR, ...)) +
  geom_XXX()

Aesthetic attributes of a geometries (color, size, transparency, etc.) can be mapped to variables in the data or set by the user, e.g. color = binary vs. color = "pink".
Use facet_wrap() when faceting (creating small multiples) by one variable and facet_grid() when faceting by two variables.

Recreate the Bechdel Test chart

Code

# load packages
library(tidyverse)
library(scales)
library(httr2)
library(colorspace)

Code

# generate request
bechdel_req <- request("http://bechdeltest.com/api/v1") |>
  req_url_path_append("/getAllMovies")

# perform request
bechdel_resp <- bechdel_req |>
  req_perform()

Code

# extract response and convert to tibble
bechdel_df <- bechdel_resp |>
  resp_body_json() |>
  enframe(name = ".id", value = "result") |>
  # tidy into one row per film
  unnest_wider(col = result) |>
  # convert rating to factor column
  mutate(rating = factor(
    x = rating,
    levels = 0:3,
    labels = c(
      "Fewer than two women",
      "Women don't talk to each other",
      "Women only talk about men",
      "Passes Bechdel test"
    ) |>
      # ensure labels are wrapped for the plot
      str_wrap(width = 18)
  ))

# summarized values for chart
bechdel_pct <- bechdel_df |>
  count(year, rating) |>
  complete(year, rating, fill = list(n = 0)) |>
  mutate(n_pct = n / sum(n), .by = year) |>
  filter(between(year, 1970, 2023))

# labels for plot
bechdel_labels <- bechdel_pct |>
  filter(year == max(year)) |>
  # calculate midpoint for each category to center on last year
  mutate(midpoint = rev(cumsum(rev(n_pct))) - n_pct + (n_pct / 2))

# initiate ggplot object
ggplot(data = bechdel_pct, mapping = aes(x = year, y = n_pct)) +
  # area chart for change in percentages over time
  geom_area(mapping = aes(fill = rating), color = "white") +
  # add text labels directly to the chart
  geom_text(
    data = bechdel_labels,
    mapping = aes(y = midpoint, label = rating, color = rating),
    family = "Atkinson Hyperlegible",
    size = 2.5,
    hjust = 0,
    nudge_x = 1
  ) +
  # add vertical lines to visually separate decades
  geom_vline(
    xintercept = seq(from = 1970, to = 2020, by = 10), color = "white",
    linewidth = 0.25
  ) +
  # percentage labels for y axis
  scale_y_continuous(labels = label_percent()) +
  # manual color palette
  scale_fill_manual(
    values = c(darken("#21918c", amount = 0.3), "#21918c", lighten("#21918c", amount = 0.3), "#440154"),
    aesthetics = c("fill", "color"),
    guide = "none"
  ) +
  # label the chart
  labs(
    title = "The Bechdel Test over time",
    subtitle = "How women are represented in movies",
    x = NULL,
    y = NULL,
    caption = "Source: bechdeltest.com; FiveThirtyEight"
  ) +
  # allow chart contents outside of panel
  coord_cartesian(clip = "off") +
  # different base theme and font
  theme_minimal(base_family = "Atkinson Hyperlegible") +
  # customize theme elements
  theme(
    panel.grid.major = element_blank(),
    panel.grid.minor = element_blank(),
    axis.ticks.length.y = unit(1, units = "cm"),
    plot.title.position = "plot",
    plot.margin = margin(r = 50, l = 5, t = 5, b = 5)
  )