how to customize the variables shown in dropdown list

Question

I am working on a SHINY app, and I am using a dropdown menu which comes with 100 different variables. I want to show only a subset of these. I could shorten the data.frame , but I need it to be this long for other reasons. Any ideas?

Thanks for your help.

this is what I have on server.R :

output$xvar <- renderUI(selectInput('xvar',label='I want to show only certain variables here', choices = names(df),selected =  names(df)[1]))

Answer 1

Wrap the subset into a reactive and just render that:

library(shiny)

ui <- fluidPage(
  uiOutput("xvar")
)

df <- 1:100
server <- function(input, output, session) {

  dfsubset <- reactive({
    df[1:10]
  })

  output$xvar <- renderUI(selectInput('xvar',label='I want to show only certain variables here', 
                                      choices = dfsubset(),selected =  dfsubset()))
}

shinyApp(ui,server)