R Shiny - Getting the label of a radio button

Question

I am trying to extract the label of the selected option in a radio button. For example, I have a radio button called 'dist' and selected option is 'norm'

ui <- fluidPage(
  radioButtons("dist", "Distribution type:",
               c("Normal" = "norm",
                 "Uniform" = "unif",
                 "Log-normal" = "lnorm",
                 "Exponential" = "exp")),
  plotOutput("distPlot")
)

server <- function(input, output) {
  x1 = input$dist
  print(x1) # gives 'norm' but I want 'Normal'
}

shinyApp(ui, server)

I wanted to know the simplest method to implement this without using any outside construct like javascript etc.

Answer 1

First of all, the code provided does not work - the server code needs to be wrapped in observe({ ... }) in order for it to function.

As for your question - there are two ways to approach this.

1. If the options are known ahead of time and are not dynamic, you can define the list of options as a separate variable that is accessible for both the UI and the server (if the ui and server are defined in separate files, then place it in a global.R file). Then simply look up the name based on the value.

    dist_options <- c("Normal" = "norm",
                      "Uniform" = "unif",
                      "Log-normal" = "lnorm",
                      "Exponential" = "exp")
   
    ui <- fluidPage(
      radioButtons("dist", "Distribution type:", dist_options),
      plotOutput("distPlot")
    )
   
    server <- function(input, output) {
      observe({
        x1 = input$dist
        print(names(which(dist_options == x1)))
      })
    }
   
    shinyApp(ui, server)
   

2. If the options are dynamic, you will need to get involved with custom javascript code. Shiny will need to ask javascript for the label value of a specific input based on its value, and javascript will need to communicate it back to shiny.