AE 08: A custom {ggplot2} theme for Cornell

Application exercise

Modified

February 10, 2025

library(tidyverse)
library(scales)

Cornell University brand identity

Organizational branding is a set of visual and verbal elements that represent an organization. It is “how your audience perceives you” and created through “many elements, including your name, logo, tagline, website, colors, collateral, messaging, positioning, graphic elements, social media, and other outreach platforms.”¹

Cornell University maintains detailed guidelines for its brand identity. The design center provides explicit instructions for using the Cornell logo, color palette, and typography, as well as downloadable materials such as a PowerPoint template.

Suppose we wish to create a series of statistical charts to be used in a Cornell Bowers CIS² presentation, but we want to ensure they are both reproducible as well as consistent with the university’s branding. We can use the {ggplot2} package to create a custom theme that adheres to the Cornell brand identity.

Basic bar chart

Let’s create a basic chart to assist us with generating an appropriate {ggplot2} theme. Here we will use graduation trends from Cornell University from College Scorecard. In this instance, we will use a bar chart to visualize the percentage of degrees awarded for three fields of study from 2018-22.

cornell_degrees <- read_csv("data/cornell-degrees.csv")
cornell_degrees

# A tibble: 135 × 3
   field_of_study  year    pct
   <chr>          <dbl>  <dbl>
 1 Computer        1996 0.0421
 2 Computer        1997 0.0497
 3 Computer        1998 0.0581
 4 Computer        1999 0.0716
 5 Computer        2000 0.0684
 6 Computer        2001 0.0859
 7 Computer        2002 0.0745
 8 Computer        2003 0.0463
 9 Computer        2004 0.0327
10 Computer        2005 0.032 
# ℹ 125 more rows

cornell_degrees_plot <- cornell_degrees |>
  filter(year >= 2018) |>
  # prep data for specific bar plot
  mutate(
    year = factor(year),
    field_of_study = fct_reorder2(.f = field_of_study, .x = year, .y = pct)
  ) |>
  ggplot(mapping = aes(x = field_of_study, y = pct, fill = year)) +
  # ensure padding between dodged bar segments
  geom_col(position = position_dodge2(padding = 0.2)) +
  scale_x_discrete(labels = label_wrap(width = 15)) +
  # format y axis labels
  scale_y_continuous(labels = label_percent()) +
  # optimal labels for chart
  labs(
    title = "Computer degrees have surpassed Engineering at Cornell",
    subtitle = "Percentage of degrees awarded by field of study",
    x = NULL,
    y = NULL,
    fill = NULL,
    caption = "Source: College Scorecard"
  )
cornell_degrees_plot

Develop a custom Cornell theme for {ggplot2}

Based on Cornell’s brand identity, we want to ensure our theme adheres to the following requirements:

A white background with grid lines on the \(y\)-axis only.
Ensure the grid lines on the \(y\)-axis are clearly visible.
An appropriate serif font for the chart. Since the official font family is Palantino and proprietary to Adobe, we will use the free Google font Spectral instead.
The title and subtitle should be centered over the entire plot, not just the plot panel (i.e. the portion of the chart where the data is displayed).
All text must be legible, including the axis labels and legend.
Place the legend on the bottom of the plot.

In addition, we want to

Use the Cornell color palette for the fill of the bars.

Note this final requirement is not part of the theme() as defined by {ggplot2}, but requires us to modify the appropriate scale for the chart.

Your turn: Implement a Cornell-branded theme for {ggplot2} that meets the requirements outlined above.

Install the required font files first!

In order to use the Spectral font, it needs to be installed on your system. You have two choices:

If you are running R on your personal computer, download Spectral and install the font as you would any other font on your computer. Once installed, restart your R session and you should be able to use the font.
Install the font for this project only using

library(systemfonts)

require_font("Spectral", dir = "fonts")

Tip

Replace the TODO placeholders with the appropriate values. Use the {ggplot2} theme() documentation as a reference.

# cornell color palette - accent colors
cornell_pal <- c("#006699", "#6EB43F", "#F8981D", "#EF4035", "#073949")

cornell_degrees_plot +
  # change color palette
  scale_fill_TODO(values = cornell_pal) +
  # use theme_minimal() as a starting point
  theme_minimal(
    base_family = "TODO",
    base_size = TODO
  ) +
  theme(
    plot.title.position = "TODO",
    plot.title = element_text(hjust = TODO),
    plot.subtitle = element_text(hjust = TODO),
    legend.position = "TODO",
    panel.grid.major.x = TODO,
    panel.grid.minor.x = TODO,
    panel.grid.major.y = element_line(TODO),
    panel.grid.minor.y = element_line(TODO),
    axis.text = element_text(TODO),
    legend.text = element_text(TODO)
  )

Error in scale_fill_TODO(values = cornell_pal): could not find function "scale_fill_TODO"

Turn into a reusable function

Demo: Convert your Cornell theme into a reusable theme_cornell() function and test it on two different charts.

# define theme as its own function
theme_cornell <- function(
    TODO
    ) {
  TODO
}

# existing bar chart
cornell_degrees_plot +
  scale_fill_TODO(values = cornell_pal) +
  theme_cornell()

Error in scale_fill_TODO(values = cornell_pal): could not find function "scale_fill_TODO"

# line graph
cornell_degrees |>
  mutate(
    field_of_study = fct_reorder2(
      .f = field_of_study,
      .x = year,
      .y = pct
    )
  ) |>
  ggplot(aes(x = year, y = pct, color = field_of_study)) +
  geom_point() +
  geom_line() +
  scale_x_continuous(limits = c(1996, 2022), breaks = seq(1996, 2020, 4)) +
  scale_color_manual(values = cornell_pal) +
  scale_y_continuous(labels = label_percent()) +
  labs(
    x = "Graduation year",
    y = "Percent of degrees awarded",
    color = "Field of study",
    title = "Cornell University degrees awarded from 1996-2022",
    subtitle = "Only the top five fields as of 2022",
    caption = "Source: Department of Education\nhttps://collegescorecard.ed.gov/"
  ) +
  theme_cornell() +
  # still makes sense to leave the legend on the right
  theme(legend.position = "right")

Error in theme_cornell(): argument "TODO" is missing, with no default

Footnotes

Source: What is Organizational Branding?↩︎
According to the Cornell Bowers CIS brand guidelines, always refer to it as Cornell Bowers CIS or the more formal Cornell Ann S. Bowers College of Computing and Information Science or Cornell Bowers Computing and Information Science, never just CIS.↩︎