Link selectInput with sliderInput in shiny

Question

Friends, I would like my selectInput to be linked to the number of clusters that appear in my output table. In other words, it appears divided into 5 clusters. In selectInpu

Answer 1

You were really close with the update expression. All you need there is:

  observeEvent(input$Slider,{
    updateSelectInput(session,'select',
                      choices=unique(1:input$Slider))
  }) 

Another approach is to use uiOutput/renderUI. In the ui, instead of creating an empty selectInput, we can put a placeholder:

uiOutput("select_clusters")

Then in the server, we populate this placeholder:

output$select_clusters <- renderUI({
  selectInput("select", label = h3("Select the cluster"), choices = 1:input$Slider)
})

---

Edit

To make an observeEvent (or eventReactive) react to multiple inputs, wrap the inputs or reactives in c():

observeEvent(c(input$SLIDER, input$FILTER),{
    updateSelectInput(session,'select',
                      choices=unique(1:input$Slider))
  }) 

But if you need to do that, I think it makes more sense, and gives flexibility, to go with the renderUI approach. This might look something like:

output$select_clusters <- renderUI({
   req(input$slider)
   req(input$filter)

   df2 <- df[df$something %in% input$filter, ]

  selectInput("select", 
              label = h3("Select the cluster"), 
              choices = df2$something)

})

In general, with the update*Input function, you can only update an existing widget, you can't remove it. But if the number of clusters = 1, then you do not need a select input at all. With renderUI you can use an empty HTML container (div()) to 'hide' the selectInput if the conditions require it:

what_to_do <- reactive({
   req(input$Slider)
   if (input$Slider == 1) {
      x <- div() 
   } else {
      x <- selectInput("select", 
                       label = h3("Select the cluster"), 
                       choices = 1:input$Slider)
   }

return(x)
})

output$select_clusters <- renderUI({
   what_to_do()
})