many selectize inputs in RShiny connected with each other - r

Question

I'm quite a beginner in R Shiny and I would like to create many multiple selectize inputs which are connected with each other. In other words : if an item is selected in one of the selectizeinputs i would like that it disappears from the other selectizeinputs' choices.
Below is an example of what i want (does not work)
modalities <- LETTERS[1:10]
library(shiny)
app <- shinyApp(
ui = tabPanel("Change modalities",
selectizeInput("ui_mod_choose1", label=paste0("Modality 1"),choices=NULL, multiple = TRUE),
selectizeInput("ui_mod_choose2", label=paste0("Modality 2"),choices=NULL, multiple = TRUE),
selectizeInput("ui_mod_choose3", label=paste0("Modality 3"),choices=NULL, multiple = TRUE)
),
server = function(input, output, session) {
observe({
updateSelectizeInput(session,"ui_mod_choose1",choices= modalities)
updateSelectizeInput(session,"ui_mod_choose2",choices= modalities)
updateSelectizeInput(session,"ui_mod_choose3",choices= modalities)
})
}
)
runApp(app)
EDIT : Here is a solution based on Bertil Nestorius' answer
modalities <- LETTERS[1:10]
library(shiny)
app <- shinyApp(
ui = tabPanel("Change modalities",
numericInput("ui_number", label="Number of modalities",min = 1, max = 4, value=3),
uiOutput("renderui")
),
server = function(input, output, session) {
output$renderui <- renderUI({
output = tagList()
for(i in 1:input$ui_number){
output[[i]] = tagList()
output[[i]][[1]] = selectizeInput(paste0("ui_mod_choose",i), label=paste0("Modality ",i),choices=modalities, multiple = TRUE)
}
return(output)
})
lapply(
X = 1:100, ####### QUESTION HERE
FUN = function(j){
observeEvent({
input[[paste0("ui_mod_choose",j)]]
},
{
sapply(1:input$ui_number,function(i){
vecteur <- do.call(c,lapply((1:input$ui_number)[-i],function(i){input[[paste0("ui_mod_choose",i)]]}))
updateSelectizeInput(session,paste0("ui_mod_choose",i),choices= modalities[!modalities %in% vecteur],selected = input[[paste0("ui_mod_choose",i)]])
})
},
ignoreNULL = FALSE)
}
)
observeEvent({
input$ui_num
},
{
sapply(1:nput$ui_num,function(i){
updateSelectizeInput(session,paste0("ui_mod_choose",i),choice= modalities,selected=NULL)
})
}
)
}
)
runApp(app)
The only problem I have left is on the following line :
X = 1:100, ####### QUESTION HERE
See this issue for more information : lapply function using a numericInput parameter around an observeEvent in RShiny

Answer 1

To have them all interconnected I would do something like this
modalities <- LETTERS[1:10]
library(shiny)
app <- shinyApp(
ui = tabPanel("Change modalities",
selectizeInput("ui_mod_choose1", label=paste0("Modality 1"),choices=NULL, multiple = TRUE),
selectizeInput("ui_mod_choose2", label=paste0("Modality 2"),choices=NULL, multiple = TRUE),
selectizeInput("ui_mod_choose3", label=paste0("Modality 3"),choices=NULL, multiple = TRUE)
),
server = function(input, output, session) {
observe({
updateSelectizeInput(session,"ui_mod_choose1",choices= modalities)
updateSelectizeInput(session,"ui_mod_choose2",choices= modalities)
updateSelectizeInput(session,"ui_mod_choose3",choices= modalities)
})
observeEvent({
input$ui_mod_choose2
input$ui_mod_choose3
},
{
updateSelectizeInput(session,"ui_mod_choose1",choices= modalities[!modalities %in% c(input$ui_mod_choose2,input$ui_mod_choose3)],selected = input$ui_mod_choose1)
},
ignoreNULL = FALSE)
observeEvent({
input$ui_mod_choose1
input$ui_mod_choose3
},
{
updateSelectizeInput(session,"ui_mod_choose2",choices= modalities[!modalities %in% c(input$ui_mod_choose1,input$ui_mod_choose3)],selected = input$ui_mod_choose2)
},
ignoreNULL = FALSE)
observeEvent({
input$ui_mod_choose2
input$ui_mod_choose1
},
{
updateSelectizeInput(session,"ui_mod_choose3",choices= modalities[!modalities %in% c(input$ui_mod_choose2,input$ui_mod_choose1)],selected = input$ui_mod_choose3)
},
ignoreNULL = FALSE)
}
)
runApp(app)

Answer 2

Something like this?
rm(list = ls())
library(shiny)
modalities <- LETTERS[1:10]
app <- shinyApp(
ui = tabPanel("Change modalities",
selectizeInput("ui_mod_choose1", label=paste0("Modality 1"),choices= modalities, multiple = TRUE),
selectizeInput("ui_mod_choose2", label=paste0("Modality 2"),choices=NULL, multiple = TRUE),
selectizeInput("ui_mod_choose3", label=paste0("Modality 3"),choices=NULL, multiple = TRUE)
),
server = function(input, output, session) {
observe({
updateSelectizeInput(session,"ui_mod_choose2",choices = modalities[!modalities%in% input$ui_mod_choose1])
})
observe({
updateSelectizeInput(session,"ui_mod_choose3",choices = modalities[!modalities %in% c(input$ui_mod_choose1,input$ui_mod_choose2)])
})
}
)
runApp(app)