R Shiny: change the value of the multiple parameter with updateSelectInput?

Question

I would like to create a Shiny app in which the inputs that can be selected depend on the database using the updateSelectInput function. I want to display the dataframe according different types and to do so, I need to change the value of the multiple parameter in selectInput .

To be clearer, this is an example of what I am trying to do:

library(shiny)
library(shinyWidgets)
library(WDI)
library(DT)
library(dplyr)

foo <- data.frame(foo_name = c("A", "A", "B", "B", "C", "C"))
data <- cbind(head(mtcars), foo)

ui <- navbarPage(position = "static-top",

                 tabPanel(title = "Base 1",
                          fluidRow(
                            dropdownButton(

                              selectInput(
                                inputId = "choice",
                                label = "Type of data",
                                choices = c("Type X",
                                            "Type Y"),
                                selected = "Type X",
                                multiple = FALSE),
                              selectInput(inputId =  "test", 
                                             label = "Test", 
                                             choices = "",
                                          multiple = TRUE),
                              circle = TRUE, status = "primary", 
                              icon = icon("gear"), 
                              width = "300px",
                              tooltip = tooltipOptions(title = "Outils")
                            ),
                            column(width = 12,
                                   dataTableOutput("data"))
                          ))

)


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

  observe({
    if(input$choice == "Type X"){
      updateSelectInput(session,
                           inputId = "test",
                           choices = unique(data$foo_name),
                           selected = NULL)
    }
    else if(input$choice == "Type Y"){
      updateSelectInput(session,
                           inputId = "test",
                           choices = unique(data$foo_name),
                           selected = NULL,
                           multiple = FALSE)
    }
  })

  output$data <- renderDataTable({
    if(input$choice == "Type X"){
    data2 <- data %>%
      filter(foo_name %in% input$test)
    }
    else if(input$choice == "Type Y"){
      data3 <- data %>%
        filter(foo_name %in% input$test)
    }
  })

}


shinyApp(ui = ui, server = server)

As you can see, when you launch the app and when the type of data is Type X , everything works fine: the dataframe is reactively displayed according to the inputs. This works because in the selectInput function, the value of the multiple parameter is TRUE .

However, if I want to display data following Type Y , the app stops working. This is because I set the multiple parameter as FALSE .

Apparently, the updateSelectInput function does not accept that we change the value of the multiple parameter. Is there a way to bypass it?

Answer 1

As ben pointed out, replacing selectInput and updateSelectInput by selectizeInput and updateSelectizeInput works. That means that I must remove multiple = FALSE and add options = list(maxItems = 1) instead, as explained here .

Here's the fixed code:

library(shiny)
library(shinyWidgets)
library(WDI)
library(DT)
library(dplyr)

foo <- data.frame(foo_name = c("A", "A", "B", "B", "C", "C"))
data <- cbind(head(mtcars), foo)

ui <- navbarPage(position = "static-top",

                 tabPanel(title = "Base 1",
                          fluidRow(
                            dropdownButton(

                              selectInput(
                                inputId = "choice",
                                label = "Type of data",
                                choices = c("Type X",
                                            "Type Y"),
                                selected = "Type X",
                                multiple = FALSE),
                              selectizeInput(inputId =  "test", 
                                             label = "Test", 
                                             choices = "",
                                          multiple = TRUE),
                              circle = TRUE, status = "primary", 
                              icon = icon("gear"), 
                              width = "300px",
                              tooltip = tooltipOptions(title = "Outils")
                            ),
                            column(width = 12,
                                   dataTableOutput("data"))
                          ))

)


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

  observe({
    if(input$choice == "Type X"){
      updateSelectizeInput(session,
                           inputId = "test",
                           choices = unique(data$foo_name),
                           selected = NULL)
    }
    else if(input$choice == "Type Y"){
      updateSelectizeInput(session,
                           inputId = "test",
                           choices = unique(data$foo_name),
                           selected = NULL,
                           options = list(maxItems = 1))
    }
  })

  output$data <- renderDataTable({
    if(input$choice == "Type X"){
    data2 <- data %>%
      filter(foo_name %in% input$test)
    }
    else if(input$choice == "Type Y"){
      data3 <- data %>%
        filter(foo_name %in% input$test)
    }
  })

}


shinyApp(ui = ui, server = server)