Shiny Web Apps

Shiny is an R package that makes it easy to build interactive web apps straight from R.

You can host

• standalone apps on a webpage
• embed them in R Markdown documents
• build dashboards

I highly recommend you to visit https://shiny.rstudio.com/ for the documentation and gallery.

Host

There are multiple way to host a shiny app.

• Install shiny server on a computer that you own
• Upload your app to https://www.shinyapps.io/
  • Each month you have 25 free active hours
  • Maximum 5 apps for free
• Google Cloud Run: https://code.markedmondson.me/shiny-cloudrun/

First Shiny App

There are couple ways to create an shiny app (we are going to focus on RStudio).

• File -> New File -> Shiny Web App
  • Single file (recommended)
  • Multiple files (essentially the same as single file, but two files)
• File -> New File -> R Markdown -> Shiny
• File -> New File -> R Markdown -> From Template -> Flex Dashboard (if flexdashboard was installed.)

Basic Struture

ui <- fluidPage(
  # controls the layout and content of the application
)


server <- function(input, output) {
  # controls the interaction, modify output based on user input
}

# run the application 
shinyApp(ui = ui, server = server)

We are going to use the tutorial in https://github.com/rstudio-education/shiny.rstudio.com-tutorial

Input and Output

Input
checkboxInput
dateInput
dateRangeInput
fileInput
numericInput
selectInput
varSelectInput
sliderInput
textInput
textAreaInput
passwordInput

Output	Render
uiOutput	renderUI
imageOutput	renderImage
plotOutput	renderPlot
tableOutput	renderTable
dataTableOutput	renderDataTable
textOutput/verbatimTextOutput	renderText/renderPrint

Reactivity

Reactivity maybe the most challenging part of learning shiny!

• reactive()
• observe() and observeEvent()
• eventReactive()
• isolate()
• reactiveVal() and reactiveValues()
• req() and need()

Basic HTML elements

https://www.learn-html.org/en/Basic_Elements