Force no default selection in selectInput()

Question

The Shiny documentation mentions that for selectInput():

selected The value (or, if none was supplied, the title) of the naviga

Answer 1

A workaround would be to use updateSelectInput. The point here is that you set your selected = argument to length(your_vector_with_choices).

You can create a reactiveValues if you want your selectInput to be updated at the very beginning (in that case only observed at program start).

library(shiny)

shinyApp(
  ui = fluidPage(
    selectInput("state", "Choose a state:", NULL),
    textOutput("result")
  ),
  
  server = function(input, output, session) {
    values <- reactiveValues(start = NULL)
    
    observe({
      choiceList <- list(`East Coast` = list("NY", "NJ", "CT"),
                         `West Coast` = list("WA", "OR", "CA"),
                         `Midwest` = list("MN", "WI", "IA"))
      updateSelectInput(session, "state", choices = choiceList, selected = choiceList[length(choiceList)])
    })
    
    output$result <- renderText({
      paste("You chose", input$state)
    })
  }
)