Introduction to Shiny

2024-12-16

Motivation

https://rconnect.dfci.harvard.edu/covidpr/

Motivation

What is Shiny?

Shiny is an R package for building interactive web applications.
Combines the computational power of R with the interactivity of modern web technologies.
No web development experience required!

Why Use Shiny?

Create interactive dashboards for data visualization.
Share R analyses with non-programmers.
Integrate real-time data updates in your workflows.

Basic Components

UI: Defines the layout and appearance of the app.
Server: Contains the logic and computations of the app.
App: Combines the UI and server into a functional app.

Basic Components

library(shiny)

# Define UI
ui <- fluidPage(
  titlePanel("Hello, Shiny!"),
  
  sidebarLayout(
    sidebarPanel(
      sliderInput("num", "Choose a number:", 1, 100, 50)
    ),
    mainPanel(
      textOutput("result")
    )
  )
)

# Define Server
server <- function(input, output) {
  output$result <- renderText({
    paste("You selected:", input$num)
  })
}

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

Example: Interactive Plot

App Overview

A scatter plot with customizable inputs.

UI Code

ui <- fluidPage(
  titlePanel("Interactive Plot"),
  sidebarLayout(
    sidebarPanel(
      sliderInput("points", "Number of Points:", 10, 1000, 500),
      selectInput("color", "Point Color:", c("Red", "Blue", "Green"))
    ),
    mainPanel(
      plotOutput("scatterPlot")
    )
  )
)

Server Code

server <- function(input, output) {
  output$scatterPlot <- renderPlot({
    plot(
      x = rnorm(input$points),
      y = rnorm(input$points),
      col = input$color,
      pch = 19
    )
  })
}

Combine UI and server using shinyApp(ui, server).

Advanced Features

Reactive Programming

reactive(): Generates a reactive expression.

reactiveVal <- reactive({
  input$num * 2
})

observe(): Executes code in response to changes.

observe({
  print(input$slider)
})

observeEvent(): Triggers on specific input changes.

observeEvent(input$button, {
  showNotification("Button clicked!")
})

Deployment Options

Share Shiny apps using:
- Shiny Server
- RStudio Connect
- shinyapps.io