combine two selectbox values in r shiny

Question

I need to combine two select box values in R shiny. Select box 1 have year, select box 2 have month.

If user select 2018 and 06, I should get 2018-06 into a variable.

I tried paste(input$year,input$month,sep="-") But it is not working.

Answer 1

This should do, note that I changed from reative to reactiveValues as I think this should be more intutive for you where you can use the v$value which will contain what you want. I suggest you have a read over https://shiny.rstudio.com/articles/reactivity-overview.html so you have a better grasp of what is happening

library(shiny)

ui <- fluidPage(
  textOutput("value"),
  selectInput("year","year",choices = c(2017,2018),selected = 1),
  selectInput("month","month",choices = c(1:12),selected = 1)

)

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

  v <- reactiveValues(value=NULL)

  observe({
    year <- input$year
    month <- input$month
    if(nchar(month)==1){
      month <- paste0("0",month)
    }
    v$value <- paste(year,month,sep="-")
  })

  output$value <- renderText({
    v$value
  })
}

shinyApp(ui, server)