R shiny: test numericInput by using logical operator

Question

In the shiny app a number can be entered (numericInput). A method should make sure that if the number equals to 1 it stays 1, but in all other cases (x!=1) the variable has to be set to 0.

in server.r:

...    
checkNumber=reactive({
      if(!is.null(input$data)){    

      output$n_insertNumber<-renderUI({
        if(!is.null(input$data)){
          numericInput("number", "Number", value = 8)
        }  
      })

      x<-input$number
      if (x!=1){x==0}
      }
})
...

in ui.r:

...    
uiOutput("n_insertNumber"),
...

Output:

Warning: Error in if: argument is of length zero

Can someone help me to find a solution? Thanks!

Answer 1

In this example app you can input a number with numericInput widget which then goes to the server and within a reactive environment a test is made. Its result is either 1 or 0 and is accessible via Variable().

---

library(shiny)

ui <- shinyUI(fluidPage(

   titlePanel("Example"),

   sidebarLayout(
      sidebarPanel(
         numericInput("number", "Number", value = 8)
      ),

      mainPanel(
         verbatimTextOutput("n_insertNumber")
      )
   )
))

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

  Variable <- reactive({
    ifelse(test = input$number == 1, yes = 1, no = 0)
  })

   output$n_insertNumber <- renderPrint({
     Variable()
   })
})


shinyApp(ui = ui, server = server)