I would like to allow multiple selection in my shiny app, and display the filtered dataset.
The code is as below:

library(shiny)
library(ggplot2)  
library(dplyr)  

result_table  = mtcars

fluidPage(
  tabsetPanel(
    tabPanel("Import data",
      titlePanel("Test"),
      
      # Create a new Row in the UI for selectInputs
      fluidRow(
        column(4,
               selectInput("cyl",
                           "cyl:",
                           c("All",
                             unique(as.character(result_table$cyl)))
                          )
        ),
        column(4,
               selectInput("vs",
                           "vs:",
                           c("All",
                             unique(as.character(result_table$vs))),
                           multiple = T)
        ),
        
      ),
      # Create a new row for the table.
      DT::dataTableOutput("table")
    ),
    tabPanel("test2",
      titlePanel("test"),
      
      # Create a new Row in the UI for selectInputs
      fluidRow(
        column(4,
               selectInput("cyl",
                           "cyl:",
                           c("All",
                             unique(as.character(result_table$cyl)))
                          )
        ),
        column(4,
               selectInput("vs",
                           "vs:",
                           c("All",
                             unique(as.character(result_table$vs))),
                           multiple = T)
        ),
      )
   )
 )
)


# Load the ggplot2 package which provides
# the 'mpg' dataset.
library(ggplot2)

function(input, output) {
  
  # Filter data based on selections
  output$table <- DT::renderDataTable(DT::datatable({
    data <- result_table 
    if (input$cyl!= "All") {
      data <- data[data$cyl== input$cyl,]
    }
    if (!(input$vs%in%  "All")) {
      data <- data[(data$vs%in% input$vs),]
    }
    data
  }))
  
}

When I run the code, the following error popped up:

I suspected that the error appeared because of if function in the server side…But I cannot figure out the reason. Maybe the format of input is not the same as data?

Please give me some suggestions. Thank you.

>Solution :

There are two issues with your code. First, when using multiple=TRUE the selected= argument defaults to no value. That’s why you an error as input$vs is NULL when you start your app. To prevent that set a selected value or account for the case of a NULL value in your server. Second, all input ids have to be unique, whereas you used the same ids for the selectInputs in both tabPanels. Hence, I renamed them to XXX2.

library(shiny)

result_table <- mtcars

ui <- fluidPage(
  tabsetPanel(
    tabPanel(
      "Import data",
      titlePanel("Test"),

      # Create a new Row in the UI for selectInputs
      fluidRow(
        column(
          4,
          selectInput(
            "cyl",
            "cyl:",
            c(
              "All",
              unique(as.character(result_table$cyl))
            )
          )
        ),
        column(
          4,
          selectInput("vs",
            "vs:",
            c(
              "All",
              unique(as.character(result_table$vs))
            ),
            selected = "All",
            multiple = TRUE
          )
        ),
      ),
      # Create a new row for the table.
      DT::dataTableOutput("table")
    ),
    tabPanel(
      "test2",
      titlePanel("test"),
      fluidRow(
        column(
          4,
          selectInput(
            "cyl2",
            "cyl:",
            c(
              "All",
              unique(as.character(result_table$cyl))
            )
          )
        ),
        column(
          4,
          selectInput("vs2",
            "vs:",
            c(
              "All",
              unique(as.character(result_table$vs))
            ),
            selected = "All",
            multiple = TRUE
          )
        ),
      )
    )
  )
)

server <- function(input, output) {
  # Filter data based on selections
  output$table <- DT::renderDataTable(DT::datatable({
    data <- result_table
    if (input$cyl != "All") {
      data <- data[data$cyl == input$cyl, ]
    }
    if (!(input$vs %in% "All")) {
      data <- data[data$vs %in% input$vs, ]
    }
    data
  }))
}

shinyApp(ui, server)
#> 
#> Listening on http://127.0.0.1:8331