How to create variable inside Taglist environment Shiny

Question

I am building a shiny dashboard with different input widgets. I want the options given in one widget to be dependent on the input in previous widget. For example, I have a pickerInput item where one can specify a variable from my dataset ( df ). Next, I want to display checkboxGroupInput where you can select the unique values of the earlier chosen variable. Therefore, the choices variable in checkboxGroupInput should be a list containing all unique values from the earlier chosen variable. My code now looks like this:

 tagList(
     pickerInput(inputId = "select_add",
                 label = "Select variable:",
                 choices = list(grouplist_1),
                 selected = NULL
                ),

                list_members = c(unique(as.data.frame(df)[input$select_add])),

                conditionalPanel(condition = "input.Name_add_member1.length > 0",
                                 checkboxGroupInput(inputId = "def_members", label = "Define",
                                 choices = list_members)

 )

In the code, the list members generates a list with the unique values in the chosen variable. However, it looks like this line is not executed here. Does anyone know how to solve this?

Answer 1

The code that filters the df to create list_members needs to be in the server part of your Shiny app, because it involves computation using one of your inputs ( input$select_add ). You can create your checkbox group dynamically using renderUI() .

ui <- fluidPage(tagList(
  uiOutput("variables"),

  conditionalPanel(condition = "input.Name_add_member1.length > 0",
                   uiOutput("members"))

))

server <- function(input, output, session) {
  df <- ... # df needs to be defined on the server side or in the global environment

  output$variables <- renderUI({
    pickerInput(
      inputId = "select_add",
      label = "Select variable:",
      choices = colnames(df),
      selected = NULL
    )
  })

  output$members <- renderUI({
    list_members = c(unique(as.data.frame(df)[input$select_add]))
    checkboxGroupInput(inputId = "def_members",
                       label = "Define",
                       choices = list_members)
  })
}

Keep in mind that df needs to be in the global environment and/or in the server() namespace.