1  Introduction to Shiny

GitHub repo folder with example R scripts for creating Shiny apps

There is a wide array of online materials that provide extensive descriptions of Shiny. Rather than reinvent the wheel, please refer to the list of resources from the Materials page. The Shiny for R tutorial and Mastering Shiny are good places to start.

Exercise 1

Code for Exercise 1

library(shiny)
library(bslib)

# Define user interface (UI)
ui <- page_sidebar(
  title = "My app",
  sidebar = sidebar(
    title = "Inputs"
  ),
  "Main content area for outputs"
)

# Define server
server <- function(input, output, session) {
  
  # Add code here for doing computations and producing output
}


# Run app
shinyApp(ui, server)

Using the {bslib} Shiny app skeleton:

1. Change title to “Skeleton Shiny app”
2. Add a brief sentence to place under the sidebar title
3. Change the text shown for the main panel

Solution for Exercise 1

library(shiny)
library(bslib)

# Define user interface (UI)
ui <- page_sidebar(
  title = "Skeleton Shiny app",
  sidebar = sidebar(
    title = "Inputs",
    "Additional info providing context to the widgets and/or app use."
  ),
  "Main content area for outputs, which can include plots, images, tables, and text!"
)

# Define server
server <- function(input, output, session) {
  
  # Add code here for doing computations and producing output
}


# Run app
shinyApp(ui, server)

Exercise 2

Code for Exercise 2

library(palmerpenguins)
library(ggplot2)
library(shiny)
library(bslib)


# Define UI
ui <- page_sidebar(
  title = "Penguins dashboard",
  
  # Define sidebar inputs
  sidebar = sidebar(
    title = "Histogram controls",
    
    #create dropdown selection for numeric columns
    varSelectInput(
      inputId = _____,
      label = "Select variable",
      data = dplyr::select_if(penguins, is.numeric)
    ),
    
    #create slider input for histogram
    sliderInput("bins", "Number of bins", min = 3, max = 100, value = 30, step = 1)
  ),  #close sidebar
  
  # Main panel content
  plotOutput("figure")
  
)  #close page_sidebar



# Define server
server <- function(input, output, session) {
  
  # Create histogram based on selection from inputs
  output$_____ <- renderPlot({
    ggplot(penguins) +
      geom_histogram(aes(!!input$variable), color = "black", fill = "cadetblue",
                     bins = input$bins) +
      theme_bw(base_size = 20)
  })
  
}


# Run app
shinyApp(ui, server)

Using the included code:

1. Fill in the blank for the missing inputId
2. Fill in the blank for the missing output object
3. Change the slider values to have a minimum of 2, maximum of 10, and a default starting value of 5

Solution for Exercise 2

library(palmerpenguins)
library(ggplot2)
library(shiny)
library(bslib)


# Define UI
ui <- page_sidebar(
  title = "Penguins dashboard",
  
  # Define sidebar inputs
  sidebar = sidebar(
    title = "Histogram controls",
    
    #create dropdown selection for numeric columns
    varSelectInput(
      inputId = "variable",
      label = "Select variable",
      data = dplyr::select_if(penguins, is.numeric)
    ),
    
    #create slider input for histogram
    sliderInput("bins", "Number of bins", min = 2, max = 10, value = 5, step = 1)
  ),  #close sidebar
  
  # Main panel content
  plotOutput("figure")
  
)  #close page_sidebar



# Define server
server <- function(input, output, session) {
  
  # Create histogram based on selection from inputs
  output$figure <- renderPlot({
    ggplot(penguins) +
      geom_histogram(aes(!!input$variable), color = "black", fill = "cadetblue",
                     bins = input$bins) +
      theme_bw(base_size = 20)
  })
  
}


# Run app
shinyApp(ui, server)