SelectInput Value update based on previous SelectInput in R shiny

Question

The R shiny script below creates three selectInputs such that the values of each selectInput depend upon the input value of the previous selectInput. E.g. in the data in the script, "value" column values depend on "Candy" column and "Candy" column values depend on the "Brand". The issue is that, whether I select "Mars" or "Netle" value in the "Brand" column, The corresponding "Candy" value "100Grand" is same for both, hence I do not see a change in the value column as the selectInput is reading the same value. Kindly help me to fix this, also please ensure the script does not become slow.

candyData <- read.table(
text = "
Brand       Candy           value
Mars        100Grand        Choc1
Netle       100Grand        Choc2
Nestle      Crunch          Choc3",
header = TRUE,
stringsAsFactors = FALSE)
library(shiny)
library(shinydashboard)
submenuUI <- function(id) {
ns <- NS(id)
tagList(
box(title = "Data", status = "primary", solidHeader = T, width = 12,
    fluidPage(
      fluidRow(
        
        column(2,offset = 0, style='padding:1px;',
               
selectInput(ns("Select1"),"select1",unique(candyData$Brand))),
        column(2,offset = 0,
              
style='padding:1px;',selectInput(ns("Select2"),"select2",choices = NULL)),
        column(2, offset = 0,
             
style='padding:1px;',selectInput(ns("Select3"),"select3",choices=NULL ))
      )))
)
}
submenuServ <- function(input, output, session){
observeEvent(input$Select1,{
updateSelectInput(session,'Select2',
choices=unique(candyData$Candy[candyData$Brand==input$Select1]))
})
observeEvent(input$Select2,{
updateSelectInput(session,'Select3',
choices=unique(candyData$value[candyData$Brand==input$Select1 &
candyData$Candy==input$Select2]))
})
}
ui <- dashboardPage(
dashboardHeader(),
dashboardSidebar(
sidebarMenu(
  shinyjs::useShinyjs(),
  id = "tabs",
  menuItem("Charts", icon = icon("bar-chart-o"),
           shinyjs::hidden(menuSubItem("dummy", tabName = "dummy")),
           menuSubItem("Sub-item 1", tabName = "subitem1")
  ))),
dashboardBody(
tabItems(tabItem("dummy"),
         tabItem("subitem1", submenuUI('submenu1'))
)
))
server <- function(input, output,session) {
callModule(submenuServ,"submenu1")
}
shinyApp(ui = ui, server = server)

qfazille · Accepted Answer · 2019-07-18 08:08:38Z

5

You can just add input$Select1 in your observeEvent to update select3

submenuServ <- function(input, output, session){
    observeEvent(input$Select1,{
        updateSelectInput(session,'Select2',
                          choices=unique(candyData$Candy[candyData$Brand==input$Select1]))
    })
    observeEvent(c(input$Select1, input$Select2),{
        updateSelectInput(session,'Select3',
                          choices=unique(candyData$value[candyData$Brand==input$Select1 &
                                                             candyData$Candy==input$Select2]))
    })
}

If you want, you can convert the observeEvent to observe :

observe({
    updateSelectInput(
        session, 'Select3',
        choices= unique(candyData$value[candyData$Brand==input$Select1 & candyData$Candy==input$Select2])
    )
})

edited Jul 18, 2019 at 8:08

answered Jan 30, 2018 at 11:00

qfazille

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2 Comments

René Nyffenegger Over a year ago

I am not sure how to understand And then you can just transform your observeEvent to observe.

qfazille Over a year ago

observeEvent & observe are actually the same. The only difference is that you choose the reactive expression that triggers your context for an observeEvent whereas every reactive expression inside an observer will trigger the context.

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