Prevent Select Input From Resetting With Streaming Data Updates

Question

I am trying to come up with a way to prevent a select input from resetting when the data it depends upon changes. Ideally, as more data arrives, the choices expand, silently, without visual disruption or input value resetting. I've tried using updateSelectInput, but without success. I've created an example that reasonably approximates my problem, have left in my comments and ideas to show where I tried to come up with a solution, and am hoping someone else has a better idea they can share. As always, thank you in advance. -nate

library(shiny)

if (interactive()) {

ui <- fluidPage(

  titlePanel("Is It Possible To Prevent The Select Input From Resetting with New Data Arriving?"),


  sidebarLayout(
      sidebarPanel(
      shiny::uiOutput(outputId = "streaming_select")
    ),

    mainPanel(
    tableOutput("table")
    )
  )
)

server<- function(input, output, session){

  session_launched<- reactiveValues(count=1)
  fake_global_rv_list<- reactiveValues()
  fake_global_rv_list$tmp<- data.frame(glob_0001=runif(10))
  session_rv_list<- reactiveValues()
  session_rv_list$tmp<- data.frame(sess_0001=runif(10)) 

  # Simulating Streaming Data every 7 seconds
  shiny::observe({
    shiny::invalidateLater(millis = 7000)
    shiny::isolate({
      shiny::showNotification(ui = "Generating Random Data", type = "default", duration = 3)
      tmp<- data.frame(runif(10) )
      colnames(tmp)<- paste0("stream_",format(as.numeric(Sys.time())))
      session_rv_list$tmp<- cbind(session_rv_list$tmp,  tmp) # Put the random data into the reactive Values list
    }) 

  })

  full_dat<- shiny::reactive({ cbind(fake_global_rv_list$tmp,  session_rv_list$tmp) })


  # Table of 'Streaming' Data 
  output$table <- renderTable({
    full_dat()
  })

  ## Select Input that let's you pick a single column
  output$streaming_select<- shiny::renderUI({
    if(!is.null(full_dat())){
      if(session_launched$count==1){
        out<- shiny::selectizeInput(inputId = "streaming_select_input", label="Pick A Column", choices = unique(colnames(full_dat())), selected = NULL, multiple = TRUE)
      } 
    }
  })
  ## Possible Ideas (?) BELOW

  # select_choices<- shiny::eventReactive(full_dat(), {
  #   if(!is.null(full_dat())){
  #     if(session_launched$count==1){
  #       out<- list( choices = unique(colnames(full_dat())), selected = NULL)
  #       #shiny::selectizeInput(inputId = "streaming_select_input", label="Pick A Column", choices = unique(colnames(full_dat())), selected = NULL, multiple = TRUE)
  #       session_launched$count<- 2
  #       return(out)
  #     } else if(session_launched$count > 1){
  #       old_selections<- input$streaming_select_input
  #       out<- list( choices = unique(colnames(full_dat())), selected = old_selections)
  #       return(out)
  #       #shiny::updateSelectizeInput(session, inputId = "streaming_select_input", choices = unique(colnames(full_dat())), selected = old_selections)
  #     }
  #   }
  # })
  # observeEvent(select_choices(), {
  #   cat("STR of select_choices is...", "\n")
  #   cat(str(select_choices()), "\n")
  # })
  # 

  # shiny::observeEvent(full_dat(), {
  #   if(session_launched$count != 1){
  #     old_selections<- input$streaming_select_input
  #     shiny::updateSelectizeInput(session, inputId = "streaming_select_input", choices = unique(colnames(full_dat())), selected = old_selections)
  #   }
  # })


}

shinyApp(ui, server)

}

Answer 1

Below is an example that works. I create the selectizeInput in the ui part, and update it on change of the full_dat data frame using an observeEvent. I had to store and reset the selection in this update step to prevent it from being set to NULL.

library(shiny)

if (interactive()) {

  ui <- fluidPage(

    titlePanel("Is It Possible To Prevent The Select Input From Resetting with New Data Arriving?"),


    sidebarLayout(
      sidebarPanel(
        shiny::selectizeInput(inputId = "streaming_select_input", label="Pick A Column",
                               choices = NULL,
                               selected = NULL,
                               multiple = TRUE)
      ),

      mainPanel(
        tableOutput("table")
      )
    )
  )

  server<- function(input, output, session){

    session_launched<- reactiveValues(count=1)
    fake_global_rv_list<- reactiveValues()
    fake_global_rv_list$tmp<- data.frame(glob_0001=runif(10))
    session_rv_list<- reactiveValues()
    session_rv_list$tmp<- data.frame(sess_0001=runif(10)) 

    # Simulating Streaming Data every 7 seconds
    shiny::observe({
      shiny::invalidateLater(millis = 7000)
      shiny::isolate({
        shiny::showNotification(ui = "Generating Random Data", type = "default", duration = 3)
        tmp<- data.frame(runif(10) )
        colnames(tmp)<- paste0("stream_",format(as.numeric(Sys.time())))
        session_rv_list$tmp<- cbind(session_rv_list$tmp,  tmp) # Put the random data into the reactive Values list
      }) 

    })

    full_dat<- shiny::reactive({ cbind(fake_global_rv_list$tmp,  session_rv_list$tmp) })


    # Table of 'Streaming' Data 
    output$table <- renderTable({
      full_dat()
    })

    ## Select Input that let's you pick a single column
    observeEvent(full_dat(), {
      selectedCols <- input$streaming_select_input
      updateSelectizeInput(session, "streaming_select_input", choices = colnames(full_dat()), selected = selectedCols)
    })
  }

  shinyApp(ui, server)

}