Get the name in selectInput widget in R shiny - html

Question

I'm using the selectInput function of shiny package with option groups like this Output of the selectInput function
In the ui.r file i've something like that:
ListOfItemsWithNames = list(condition = c("KO","WT"),treatment = c("non","oui"))
selectInput("Select1_contrast",label="Compare",ListOfItemsWithNames)
In the server.R file, when i call input$Select1_contrast I only get the selected value ("oui" for instance).
Is there a way to get both the value an the name of the variable (ie, "oui" and "treatment") ?

Answer 1

Here is another possibility. It uses key-value pairs. Those pairs are allowed according to the documentation of selectInput
choices List of values to select from. If elements of the list are named, then that name rather than the value is displayed to the user. This can also be a named list whose elements are (either named or unnamed) lists or vectors. If this is the case, the outermost names will be used as the "optgroup" label for the elements in the respective sublist. This allows you to group and label similar choices. See the example section for a small demo of this feature.
addKeys = function(nested_list){
keyed_nl = list()
for (a in names(nested_list))
for (b in (nested_list[[a]]))
keyed_nl[[a]][[b]] = paste0(a, "-", b)
keyed_nl
}
ListOfItemsWithNames = list(condition = c("KO", "WT"),
treatment = c("non", "oui"))
keyedList = addKeys(ListOfItemsWithNames)
library(shiny)
shinyApp(
fluidPage(
selectInput("choiceKey", "choose", keyedList),
textOutput('text')
),
function(input, output, session)
output$text = renderText(input$choiceKey)
)
As you can see, input$choiceKey will give you the category and the choice seperated with -. Using strsplit, you can get both parts seperately

Answer 2

This should work. In this version, you have a sencond dropdown menu and therefore a second input.
library(shiny)
ListOfItemsWithNames = list(condition = c("KO","WT"),treatment = c("non","oui"))
ui = inputPanel(
selectInput("category", "choose a category", names(ListOfItemsWithNames )),
selectInput("choice", "select a choice", ListOfItemsWithNames[[1]])
)
server = function(input, output, session){
observe({
updateSelectInput(session, "choice",
choices = ListOfItemsWithNames[[input$category]])
})
}
shinyApp(ui, server)