R shiny favourites in long selectInput lists - r

Question

How do I deal with long lists of options? In the example below, I have a subset of the options as favourites, but want to be able to select all options including the non-favourites. How do I get the input$selected to return what I selected last based on both the radiogroupbutton() and the selectInput()?
EDIT: I would like to keep the look, which has radiobuttons AND a drop down list. Therefore, I assume both will need different inputID's which then could be combined (somehow) in the server site (as Joris suggested). I am not sure how to combine them on the server site, and how to identify what was selected last.
ALL.options <- apply(expand.grid(LETTERS, LETTERS), 1, function(x){paste(x, collapse="")})
favourites <- sample(ALL.options, 20)
ui <- fluidPage(
h3("Favourites:"),
radioGroupButtons(inputId="selected",
choices = sort(favourites),
individual = TRUE,
selected = NULL,
width="20%"),
selectInput(inputId="selected", label = "Other options",
choices = ALL.options,
selected = NULL),
h3("THIS IS YOUR SELECTION:"),
verbatimTextOutput("choice")
)
)
server <- function(input, output) {
output$choice <- renderPrint(
input$selected
)
}
shinyApp(ui, server)

Answer 1

Perhaps it suffices to use a single selectInput or selectizeInput that lists the Favourites and Other options in separate option groups (see e.g. Shiny: Option groups for selectize input):
library(shiny)
ALL.options <- apply(expand.grid(LETTERS, LETTERS), 1, function(x){paste(x, collapse="")})
favourites <- sample(ALL.options, 20)
ui <- fluidPage(
selectizeInput(inputId = "selected", label = "All options", choices = list(
Favourites = favourites,
`Other options` = setdiff(ALL.options, favourites)
),
options = list(
placeholder = '<None selected>',
onInitialize = I('function() { this.setValue(""); }')
)
),
h3("THIS IS YOUR SELECTION:"),
verbatimTextOutput("choice")
)
server <- function(input, output) {
output$choice <- renderPrint({
validate(need(input$selected, "None selected"))
input$selected
})
}
shinyApp(ui, server)
NB: If you instead use two separate inputs (radioGroupButtons and selectInput) you could combine the selected choices server-side in a reactive object. For instance:
library(shiny)
library(shinyWidgets)
ALL.options <- apply(expand.grid(LETTERS, LETTERS), 1, function(x){paste(x, collapse="")})
favourites <- sample(ALL.options, 20)
ui <- fluidPage(
h3("Favourites:"),
radioGroupButtons(inputId = "radio",
choices = sort(favourites),
individual = TRUE,
selected = character(0),
width="20%"),
selectizeInput(inputId="select", label = "Other options",
choices = ALL.options,
options = list(
placeholder = '<None selected>',
onInitialize = I('function() { this.setValue(""); }')
)
),
h3("THIS IS YOUR SELECTION:"),
verbatimTextOutput("choice")
)
server <- function(input, output) {
## initialize reactive value
currentSelected <- reactiveVal(NULL)
## update based on radioGroupButtons
observeEvent(input$radio, {
currentSelected(input$radio)
})
## update based on selectInput
observeEvent(input$select, {
currentSelected(input$select)
})
output$choice <- renderPrint({
validate(need(currentSelected(), "None selected"))
currentSelected()
})
}
shinyApp(ui, server)
Created on 2019-06-17 by the reprex package (v0.3.0)

Answer 2

I am not sure if I understand fully what you are trying to achieve. I also notice that both the radioGroupButtons and the selectInput have the same inputId. If the idea is to print both the choices, you could change the inputId of the selectInput to say, select and just modify the renderPrint as:
output$choice <- renderPrint(
c(input$selected, input$select)
)
Is this what you are looking for?