Make renderUI an input for observeEvent

Question

As the title suggests, I wish to make a dynamically created UI object (using renderUI) which can be further manipulated later in the Shiny App.

In the below reprex, I have a toy application which allows a user to filter the iris dataset based on the sepal width. Depending on the range the user selects, I then generate a checkbox list of all the unique species within that sepal width range.

My question is: how can I make the app tell me which species' checkbox has been selected once the user has filtered the table? For example, at the default app settings when the sepal width range is between 1 and 2, only one species is satisfies the filter requirement (versicolor). When a user checks the versicolor box, I would like the app to update to tell me that versicolor has been selected.

Similarly, when the sepal width range is greater (and more species are then included in the dynamically generated checkbox list) I would like the UI to update again to tell me which species was selected (either 1, 2 or all 3 species).

The basic workflow in my head is:

(1) User filters Dataset (2) Displayed Table Updates Based on Filter (3) App Generates Checkbox List of Unique Species (4) User Clicks on Species, Species Name is Presented on-screen.

library(shiny)
library(DT)
library(dplyr)

ui <- basicPage(

  fluidRow(
    uiOutput("ui"),
    sliderInput("slider", "Sepal Width", min = 0, max=20, value=c(1:2)),
    tableOutput("data")

  ),

)



server <- function(input, output){

  data("iris")

  filtered<-reactive({

    iris %>% filter(`Sepal.Width` %in% input$slider[1]:input$slider[2])


  })

  output$data<-renderTable({

    filtered()

  })

  output$ui<-renderUI({

    species<-filtered() 
    checkboxGroupInput(inputId = 'occurence_checkboxes', label = 'Species', choices = unique(species$Species))

  })




}

shinyApp(ui, server)

Do you just expect the name of the selected species by the user to be presented on the screen ? Or making a filtering wrt the selected species by the user? — maydin
– maydin, Commented Aug 8, 2019 at 11:15
The ultimate aim is, once the species have been filtered, for downstream code to pull observation records for those species and display them on a map. As this will be reasonably computationally expensive, I didn't want the code to run unless the user explicitly wants to see where those species are distributed (by selecting the desired species). I hope that clarifies things. — Simon
– Simon, Commented Aug 8, 2019 at 11:23

thothal · Accepted Answer · 2019-08-08 11:23:04Z

2

This should do the trick:

library(shiny)
library(dplyr)

ui <- basicPage(
  fluidRow(
    uiOutput("ui"),
    sliderInput("slider", "Sepal Width", min = 0, max=20, value = 1:2),
    tableOutput("data")
  )
)

server <- function(input, output){
  get_width_filter <- reactive({
     iris %>% filter(between(Sepal.Width, input$slider[1], input$slider[2]))
  })

  get_ovl_filter <- reactive({
     get_width_filter() %>%
       filter(Species %in% input$occurence_checkboxes)
  })

  output$data <- renderTable({
    get_ovl_filter()
  })

  output$ui <- renderUI({
    choices <-  get_width_filter() %>% pull(Species) %>% unique()
    checkboxGroupInput("occurence_checkboxes", 
                       "Species", 
                       choices = choices, 
                       selected = choices)
  })
}

shinyApp(ui, server)

Explanation

We need to split the filtered routine in 2 parts: 1 which applies just the width filter and one which also incorporates the species filter. You can access the dynamically created checkbox via the name which you you use in your renderUI function. The reason that we have to split the filter reactive is that otherwise the renderUI would take dependence on the checkbox itself which we want to avoid.

Update

I just read that you just wanted to return the values of the checkbox not use it to filter. But I guess that this should be clear now, just use input$occurence_checkboxes whereever you need it.

edited Aug 8, 2019 at 11:23

answered Aug 8, 2019 at 11:16

thothal

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4 Comments

Simon Over a year ago

Thanks for the reply but I don't think this is doing quite what I expect. The ultimate aim for the app is, once the species have been filtered (using the slider), for downstream code to pull the observation records for those species and display them on a map. As this will be reasonably computationally expensive, I didn't want the code to run unless the user explicitly wants to see where those species are distributed (by selecting the desired species using the dynamically generated checkboxes). Thus I need to trigger a unique event for each checkbox selection.

Simon Over a year ago

Ah, just seen your update about input$occurrence_checkboxes. Let me have a quick play and I'll get back to you on whether this provides the necessary functionality. Cheers!

Simon Over a year ago

Hi thothal, if you get a minute would you be able to edit your answer's code to demonstrate the functionality you mention under your 'Update' (and in response to my comments to your answer). I've tried using input$occurrence_checkboxes in a manner which I thought was correct...yet I can't get the code to work. Thanks in advance.

Simon Over a year ago

Nevermind, it was a typo on my part! All working now. Accepting your answer. Thanks for your (speedy) help.

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