13.5 Inputs, outputs and reactivity

• Inputs are objects we can interact with by modifying their values such as texts, numbers or dates.

• Outputs are objects we want to show in the app and can be plots, tables or HTML widgets.

• Shiny apps use a functionality called reactivity to support interactivity. In this way, we can modify the values of the inputs, and automatically the outputs that use these inputs will change. The structure of a Shiny app that includes inputs and outputs, and supports reactivity is shown below.

ui <- fluidPage(
  *Input(inputId = myinput, label = mylabel, ...)
  *Output(outputId = myoutput, ...)
)

server <- function(input, output){
  output$myoutput <- render*({
    # code to build the output.
    # If it uses an input value (input$myinput),
    # the output will be rebuilt whenever
    # the input value changes
  })}