Interactive reporting with Shiny (I)

Lecture 19

Dr. Benjamin Soltoff

Cornell University
INFO 5001 - Fall 2025

November 4, 2025

Announcements

Announcements

  • Homework 06
  • Project drafts due November 20

Learning objectives

  • Introduce Shiny for interactive web applications
  • Review implementation of basic Shiny app
  • Distinguish the user interface from server components
  • Develop user interfaces with Shiny + {bslib}

Shiny: High level view

Every Shiny app has a webpage that the user visits,
and behind this webpage there is a computer that serves this webpage by running R (or Python!).

When running your app locally, the computer serving your app is your computer.

When your app is deployed, the computer serving your app is a web server.

Dating rules

Age gaps

Dating rules

Anatomy of a Shiny app

What’s in an app?

library(shiny)
library(bslib)

# Define UI ----
ui <- page_fillable()

# Define server logic ----
server <- function(input, output) {}

# Run the app ----
shinyApp(ui = ui, server = server)

  • User interface controls the layout and appearance of app

  • Server function contains instructions needed to build app

Inputs and outputs

  • For interactivity, app needs inputs and outputs
  • Inputs - things user can toggle/adjust
  • Output - R objects user can see, often depend on inputs

Inputs

library(shiny)
library(bslib)

# Define UI ----
ui <- page_fillable(
  sliderInput(
    inputId = "num",
    label = "Choose a number",
    min = 0,
    max = 100,
    value = 20
  )
)

# Define server logic ----
server <- function(input, output) {}

# Run the app ----
shinyApp(ui = ui, server = server)

Inputs

#| '!! shinylive warning !!': |
#|   shinylive does not work in self-contained HTML documents.
#|   Please set `embed-resources: false` in your metadata.
#| standalone: true
#| viewerHeight: 700

library(shiny)
library(bslib)

# Define UI ----
ui <- page_fillable(
  sliderInput(
    inputId = "num",
    label = "Choose a number",
    min = 0,
    max = 100,
    value = 20
  )
)

# Define server logic ----
server <- function(input, output) {}

# Run the app ----
shinyApp(ui = ui, server = server)

Inputs

sliderInput(
  inputId = "num",
  label = "Choose a number",
  min = 0,
  max = 100,
  value = 20
)
<div class="form-group shiny-input-container">
  <label class="control-label" id="num-label" for="num">Choose a number</label>
  <input class="js-range-slider" id="num" data-skin="shiny" data-min="0" data-max="100" data-from="20" data-step="1" data-grid="true" data-grid-num="10" data-grid-snap="false" data-prettify-separator="," data-prettify-enabled="true" data-keyboard="true" data-data-type="number"/>
</div>

Inputs

sliderInput(
  inputId = "num",
  label = "Choose a number",
  min = 0,
  max = 100,
  value = 20
)
  • Input name
  • Label to display
  • Input-specific arguments

Outputs

Function Outputs
plotOutput() plot
tableOutput() table
uiOutput() Shiny UI element
textOutput() text
  • Plots, tables, text - anything that R creates and users see
  • Initialize as empty placeholder space until object is created

Outputs

library(shiny)
library(bslib)

# Define UI ----
ui <- page_fillable(
  sliderInput(
    inputId = "num",
    label = "Choose a number",
    min = 0,
    max = 100,
    value = 20
  ),
  plotOutput("myplot")
)

# Define server logic ----
server <- function(input, output) {}

# Run the app ----
shinyApp(ui = ui, server = server)

Outputs

#| '!! shinylive warning !!': |
#|   shinylive does not work in self-contained HTML documents.
#|   Please set `embed-resources: false` in your metadata.
#| standalone: true
#| viewerHeight: 700

library(shiny)
library(bslib)

# Define UI ----
ui <- page_fillable(
  sliderInput(
    inputId = "num",
    label = "Choose a number",
    min = 0,
    max = 100,
    value = 20
  ),
  plotOutput("myplot")
)

# Define server logic ----
server <- function(input, output) {}

# Run the app ----
shinyApp(ui = ui, server = server)

Designing a modern UI with {bslib}

{bslib}

Modern UI toolkit for Shiny based on Bootstrap:

🔗 https://rstudio.github.io/bslib

{bslib}

value_box(
  title = "I got",
  value = "99 problems",
  showcase = bs_icon("music-note-beamed"),
  p("bslib ain't one", bs_icon("emoji-smile")),
  p("hit me", bs_icon("suit-spade"))
)

I got

99 problems

bslib ain't one

hit me

Application exercise

ae-17

Instructions

  • Go to the course GitHub org and find your ae-17 (repo name will be suffixed with your GitHub name).
  • Clone the repo in Positron, run renv::restore() to install the required packages, open the Quarto document in the repo, and follow along and complete the exercises.
  • Render, commit, and push your edits by the AE deadline – end of the day

Age rule app

Instructions

  • Navigate to the age-rule folder, and launch the app by opening the app.R file and clicking on Run App.
  • Review the UI components - how is the user interface built?
  • Close the app by clicking the stop icon

Exploring the impact of climate change

National Risk Index

Build a Shiny app for the NRI

Instructions

Wrap-up

Wrap-up

  • Shiny apps are interactive web applications built using R or Python
  • Use server-side rendering to dynamically generate content
  • Design a user interface with inputs and outputs

Acknowledgements