selectInput does not return ALL and convert factor to number in shiny

April 5, 2024

In Shiny, I want to be able to choose All when I use selectInput.

However, in the shiny app below, when I used selectInput for column Species and specified the option All for choices, shiny converted the column to number (instead of factor).

library(shiny)
library(palmerpenguins)

# Load the palmerpenguins dataset
data("penguins")

# Define UI
ui <- fluidPage(
  titlePanel("Penguin Species Selector"),
  
  sidebarLayout(
    sidebarPanel(
      selectInput("species", "Select Species:",
                  choices = c("All", unique(penguins$species))),
      hr(),
      helpText("Select a species to view its data.")
    ),
    
    mainPanel(
      tableOutput("penguin_table")
    )
  )
)

# Define server logic
server <- function(input, output) {
  output$penguin_table <- renderTable({
    if (input$species == "All") {
      return(penguins)
    } else {
      return(subset(penguins, species == input$species))
    }
  })
}

# Run the application
shinyApp(ui = ui, server = server)

When I removed All and used this choices = unique(penguins$species) (see below), the the shiny app will show the column as a factor, but now I could not choose All

library(shiny)
library(palmerpenguins)

# Load the palmerpenguins dataset
data("penguins")

# Define UI
ui <- fluidPage(
  titlePanel("Penguin Species Selector"),
  
  sidebarLayout(
    sidebarPanel(
      selectInput("species", "Select Species:",
                  choices = unique(penguins$species)),
      hr(),
      helpText("Select a species to view its data.")
    ),
    
    mainPanel(
      tableOutput("penguin_table")
    )
  )
)


# Define server logic
server <- function(input, output) {
  output$penguin_table <- renderTable({
    if (input$species == "All") {
      return(penguins)
    } else {
      return(subset(penguins, species == input$species))
    }
  })
}

# Run the application
shinyApp(ui = ui, server = server)

>Solution :

This is because factors are internally stored as numbers. If you run the code in the console it will be clear what is happening.

c("All", unique(penguins$species))
#[1] "All" "1"   "3"   "2"

A simple fix would be to to turn the species to characters while passing it into selectInput.

c("All", unique(as.character(penguins$species)))
#[1] "All"       "Adelie"    "Gentoo"    "Chinstrap"

Complete code –

library(shiny)
library(palmerpenguins)

# Load the palmerpenguins dataset
data("penguins")

# Define UI
ui <- fluidPage(
  titlePanel("Penguin Species Selector"),
  
  sidebarLayout(
    sidebarPanel(
      selectInput("species", "Select Species:",
                  choices = c("All", unique(as.character(penguins$species)))),
      hr(),
      helpText("Select a species to view its data.")
    ),
    
    mainPanel(
      tableOutput("penguin_table")
    )
  )
)

# Define server logic
server <- function(input, output) {
  output$penguin_table <- renderTable({
    if (input$species == "All") {
      return(penguins)
    } else {
      return(subset(penguins, species == input$species))
    }
  })
}

# Run the application
shinyApp(ui = ui, server = server)