Shiny frameworks

This website is a resource for developers to get an ‘under the hood’ view of three popular Shiny frameworks.

gap: a golem app-package (download gap)

lap: a leprechaun app-package (download lap)

rap: a rhino app (pseudo-package)¹ (download rap)

The application

The original data and code for each application comes from Building Web Applications With Shiny,² but has been adapted to provide a basic (but realistic) example with modules, utility function, tests, etc.

library(shiny)
library(shinythemes)
ui <- fluidPage(
  theme = shinythemes::shinytheme("spacelab"),
  sidebarLayout(
    sidebarPanel(
      selectInput(
        inputId = "y",
        label = "Y-axis:",
        choices = c(
          "IMDB rating" = "imdb_rating",
          "IMDB number of votes" = "imdb_num_votes",
          "Critics Score" = "critics_score",
          "Audience Score" = "audience_score",
          "Runtime" = "runtime"
        ),
        selected = "audience_score"
      ),
      selectInput(
        inputId = "x",
        label = "X-axis:",
        choices = c(
          "IMDB rating" = "imdb_rating",
          "IMDB number of votes" = "imdb_num_votes",
          "Critics Score" = "critics_score",
          "Audience Score" = "audience_score",
          "Runtime" = "runtime"
        ),
        selected = "critics_score"
      ),
      selectInput(
        inputId = "z",
        label = "Color by:",
        choices = c(
          "Title Type" = "title_type",
          "Genre" = "genre",
          "MPAA Rating" = "mpaa_rating",
          "Critics Rating" = "critics_rating",
          "Audience Rating" = "audience_rating"
        ),
        selected = "mpaa_rating"
      ),
      sliderInput(
        inputId = "alpha",
        label = "Alpha:",
        min = 0, max = 1,
        value = 0.4
      ),
      sliderInput(
        inputId = "size",
        label = "Size:",
        min = 0, max = 5,
        value = 3
      ),
      textInput(
        inputId = "plot_title",
        label = "Plot title",
        placeholder = "Enter text to be used as plot title"
      ),
      actionButton(
        inputId = "update_plot_title",
        label = "Update plot title"
      )
    ),
    mainPanel(
      br(),
      p(
        "These data were obtained from",
        a("IMBD", href = "http://www.imbd.com/"), "and",
        a("Rotten Tomatoes", href = "https://www.rottentomatoes.com/"), "."
      ),
      p(
        "The data represent",
        nrow(movies),
        "randomly sampled movies released between 1972 to 2014 in the United States."
      ),
      plotOutput(outputId = "scatterplot"),
      hr(),
      p(em(
        "The code for this Shiny application comes from",
        a("Building Web Applications with shiny",
          href = "https://rstudio-education.github.io/shiny-course/"
        )
      ))
    )
  )
)

server <- function(input, output, session) {
  
  new_plot_title <- reactive({
    tools::toTitleCase(input$plot_title)
  }) |>
    bindEvent(input$update_plot_title,
      ignoreNULL = FALSE,
      ignoreInit = FALSE
    )


  output$scatterplot <- renderPlot({
    scatter_plot(
      # load movies data 
      df = movies,
      x_var = input$x,
      y_var = input$y,
      col_var = input$z,
      alpha_var = input$alpha,
      size_var = input$size
    ) +
      ggplot2::labs(title = new_plot_title()) +
      ggplot2::theme_minimal() +
      ggplot2::theme(legend.position = "bottom")
  })
}

shinyApp(ui = ui, server = server)

scatter_plot() gives us an example utility function to build with our applications.

scatter_plot <- function(df, x_var, y_var, col_var, alpha_var, size_var) {
    ggplot2::ggplot(data = df,
      ggplot2::aes(x = .data[[x_var]],
          y = .data[[y_var]],
          color = .data[[col_var]])) +
      ggplot2::geom_point(alpha = alpha_var, size = size_var)

}

The application also uses an external dataset.³

Footnotes

1. rhino apps aren’t R packages–they’re dependencies are managed with a dependencies.R file and box modules.

2. This was a popular course among colleagues and covers (in my opinion) what a developer should know before considering a framework.

3. You can download the movies data here.