Change Selectize Choices But Retain Previously Selected Values

Question

Question

I have two dropdowns, the choices available in dd2 are conditional on option selected in dd1. I"m unable to figure out how to change the options of dropdown 2 but retain whatever selection has already been made. I should also be able to drop items from previous selection through dropdown 2.

Example

let's say dd1 is Country: India, England, USA and the respective options in dd2, City: (New Delhi, Mumbai), (London, Birmingham), (New York, Washington DC). I first select India, then Mumbai, then select England, retain Mumbai, and add London. Then I add New York in a similar manner. I now realise that I didn't need Mumbai so I remove it leaving me with London, New York.

Failed Attempts

I'm trying things like appending selections to previously existing vectors and passing the intersection of two vectors to the 'selected' argument but it seems to not work. I'm guessing the circular nature of doing that probably causes problems.

Basic code

To save you guys some time and allow us to have the same reference -

# server.r

library(shiny)
library(data.table)
countrycity = data.table(
country = c('India','India','England','England','USA','USA'),
city = c('New Delhi','Mumbai','London','Birmingham','New York','Washington DC')
)

shinyServer(function(input, output) {

    # dd1: country
    output$chooseCountry <- renderUI({
        selectizeInput(
           "countrSelected", 
           "Country", 
           as.list(c('All',unique(unique(countrycity$country)))),
           options = list(create = TRUE),
           selected = c('All'),
           multiple = TRUE,
           width="120px" 
        )
    })

    # filtering list of cities based on the country selected
    citiestoshow = reactive({

        countryselected = if ( is.null(input$countryselected) ) {
           unique(countrycity$country)
        } else if ( 'All' %in% input$countryselected ) {
           unique(countrycity$country)
        } else {
           input$countryselected 
        }

        countrycity[country %in% countryselected, city]

    })

    # dd2: city
    output$choosecities <- renderUI({      

        selectizeInput(
           'cityselected', 
           label = 'City', 
           choices = as.list(c('All',citiestoshow())),
           options = list(create = TRUE),
           multiple = TRUE,
           width="120px"
        )

    })


}

Answer 1

If anyone is still looking for a simple example for updating the selections while maintaining previously selected value:

#in ui.R you have a selectInput that you want to update
selectInput(inputId = "mymenu", label = "My Menu",
            choices = c("A" = "a","B" = "b","C" = "c"),
            selected = c("A" = "a"))


# in server.R create reactiveVal
current_selection <- reactiveVal(NULL)

# now store your current selection in the reactive value
observeEvent(input$mymenu, {
             current_selection(input$mymenu)
             })

#now if you are updating your menu
updateSelectInput(session, inputId = "mymenu", 
                  choices = c("A" = "a","B" = "b","C" = "c", "D" = "d"), 
                  selected = current_selection())

Answer 2

Here is one implementation that should do it (more details here):

runApp(list(ui={shinyUI(pageWithSidebar(

  headerPanel("shinyUI"),

  sidebarPanel(
    uiOutput("choose_country"),

    uiOutput("choose_city")
  ),

  mainPanel(
    headerPanel("mainPanel")
  )
))},

server={

        #Consider creating a file.

        countries <- c('India','England','USA')            
        countrycity<-list()
        countrycity[[countries[1]]]<-c('New Delhi','Mumbai')
        countrycity[[countries[2]]]<-c('London','Birmingham')
        countrycity[[countries[3]]]<-c('New York','Washington DC')

        shinyServer(function(input, output) {

          # Drop-down selection box for which data set
          output$choose_country <- renderUI({
            selectInput("choose_country", "Select Country", as.list(countries))
          })

          # Check boxes
          output$choose_city <- renderUI({
            # If missing input, return to avoid error later in function
            if(is.null(input$choose_country))
              return()

            # Get the data set with the appropriate name
            selected_country <- input$choose_country
            cities<-countrycity[[selected_country]]

            # Create the checkboxes and select them all by default
            selectInput("choose_city", "Choose city", 
                        choices  = as.list(cities))
          })

        })}
))

---

Update 1 (Keep previous selections - rough version) :

runApp(list(ui={

  library(shiny)
  #ui.R
  ui.r<-shinyUI(pageWithSidebar(

    headerPanel("shinyUI"),

    sidebarPanel(
      uiOutput("choose_country"),
      uiOutput("choose_city")
      ,actionButton('add','Add City')
    ),

    mainPanel(
      headerPanel("mainPanel")
      , checkboxGroupInput('currentselection', 'Current Selection', choices = c('None'),selected=c(''))
    )
  ))

},

server={
  library(shiny)
  #server.R
  countries <- c('India','England','USA')
  countrycity<-list()
  countrycity[[countries[1]]]<-c('New Delhi','Mumbai')
  countrycity[[countries[2]]]<-c('London','Birmingham')
  countrycity[[countries[3]]]<-c('New York','Washington DC')

  #Alphabetize (Optional)
  order_cities<-order(countries)
  countries<-countries[order_cities]
  countrycity<-countrycity[order_cities]
  countrycity<-lapply(countrycity,sort)

  server.ui<-shinyServer(function(input, output,session) {

    # Drop-down selection box for Country Selection
    output$choose_country <- renderUI({
      selectInput("choose_country", "Select Country", as.list(countries))
    })

    # City Selection
    output$choose_city <- renderUI({
      # If missing input, return to avoid error later in function
      if(is.null(input$choose_country))
        return()

      # Get the data set with the appropriate name
      selected_country <- input$choose_country
      cities<-countrycity[[selected_country]]

      # Create the drop-down menu for the city selection
      selectInput("choose_city", "Choose city", 
                  choices  = as.list(cities))
    })

    ##Keep previous selections in a session
    lvl<-reactive(unlist(input$currentselection))

    observe({
      if(input$add==0) return()
      isolate({
        current_selection<-paste(input$choose_city,input$choose_country,sep=", ")
        updateCheckboxGroupInput(session, "currentselection", choices = c(current_selection,lvl())
                                 ,selected=c(current_selection,lvl()))
      })#iso
    })#obs
    observe({
      updateCheckboxGroupInput(session, "currentselection", choices = unique(c(lvl()))
                               ,selected=c(lvl()))
    })

  })   
}
))

---

Update 2:

runApp(list(ui={

  library(shiny)
  #ui.R
  ui.r<-shinyUI(



    pageWithSidebar(
      headerPanel("shinyUI"),

      sidebarPanel(
        uiOutput("choose_country"),
        uiOutput("choose_city")
      ),

      mainPanel(
        headerPanel("mainPanel")
        #, checkboxGroupInput('currentselection', 'Current Selection', choices = c('None'),selected=c(''))
      )
    ))

},

server={
  library(shiny)
  #server.R
  countries <- c('India','England','USA')
  countrycity<-list()
  countrycity[[countries[1]]]<-c('None','New Delhi','Mumbai')
  countrycity[[countries[2]]]<-c('None','London','Birmingham')
  countrycity[[countries[3]]]<-c('None','New York','Washington DC')


  #Alphabetize (Optional)
  order_cities<-order(countries)
  countries<-countries[order_cities]
  countrycity<-countrycity[order_cities]
  countrycity<-lapply(countrycity,sort)

  server.ui<-shinyServer(function(input, output,session) {

    session$countrycitySelection<-list()
    for(country in countries){
      session$countrycitySelection[[country]]<-'None'
    }

    # Drop-down selection box for Country Selection
    output$choose_country <- renderUI({
      selectInput("choose_country", "Select Country", as.list(countries))
    })

    # City Selection
    output$choose_city <- renderUI({
      # If missing input, return to avoid error later in function
      if(is.null(input$choose_country))
        return()

      # Get the data set with the appropriate name
      selected_country <- input$choose_country
      cities<-countrycity[[selected_country]]

      # Create the drop-down menu for the city selection
      selectInput("choose_city", "Choose city", 
                  choices  = as.list(cities),selected = NULL, multiple = FALSE,
                  selectize = TRUE, width = NULL)
    })


    #changing country selection
    observe({
      country <- input$choose_country
      if(is.null(country)) return()
      isolate({
        updateSelectInput(session, "choose_city", choices = countrycity[[country]]
                          ,selected = session$countrycitySelection[[country]]   )
      })#iso
    })#obs

    #changing city selection
    observe({
      city <- input$choose_city
      if(is.null(city)) return()
      isolate({
        country<-input$choose_country
        session$countrycitySelection[[country]]<-city
      })#iso
    })#obs

  })   
}
))

---

Update 3: (2016) Shiny no longer allows adding values to session so here is the same with reactive :

runApp(list(ui={

  library(shiny)
  #ui.R
  ui.r<-shinyUI(



    pageWithSidebar(
      headerPanel("shinyUI"),

      sidebarPanel(
        uiOutput("choose_country"),
        uiOutput("choose_city")
      ),

      mainPanel(
        headerPanel("mainPanel")
        #, checkboxGroupInput('currentselection', 'Current Selection', choices = c('None'),selected=c(''))
      )
    ))

},

server={
  library(shiny)
  #server.R
  countries <- c('India','England','USA')
  countrycity<-list()
  countrycity[[countries[1]]]<-c('None','New Delhi','Mumbai')
  countrycity[[countries[2]]]<-c('None','London','Birmingham')
  countrycity[[countries[3]]]<-c('None','New York','Washington DC')


  #Alphabetize (Optional)
  order_cities<-order(countries)
  countries<-countries[order_cities]
  countrycity<-countrycity[order_cities]
  countrycity<-lapply(countrycity,sort)


  countrycitySelection<-list()
  for(country in countries){
    countrycitySelection[[country]]<-'None'
  }


  server.ui<-shinyServer(function(input, output,session) {

    values <- reactiveValues(countrycitySelection = countrycitySelection)
    # Drop-down selection box for Country Selection
    output$choose_country <- renderUI({
      selectInput("choose_country", "Select Country", as.list(countries))
    })

    # City Selection
    output$choose_city <- renderUI({
      # If missing input, return to avoid error later in function
      if(is.null(input$choose_country))
        return()

      # Get the data set with the appropriate name
      selected_country <- input$choose_country
      cities<-countrycity[[selected_country]]

      # Create the drop-down menu for the city selection
      selectInput("choose_city", "Choose city", 
                  choices  = as.list(cities),selected = NULL, multiple = FALSE,
                  selectize = TRUE, width = NULL)
    })


    #changing country selection
    observe({
      country <- input$choose_country
      if(is.null(country)) return()
      isolate({
        updateSelectInput(session, "choose_city", choices = countrycity[[country]]
                          ,selected = values$countrycitySelection[[country]]   )
      })#iso
    })#obs

    #changing city selection
    observe({
      city <- input$choose_city
      if(is.null(city)) return()
      isolate({
        country<-input$choose_country
        values$countrycitySelection[[country]]<-city
      })#iso
    })#obs

  })   
}
))