using click.dt with sliders to filter after a click not updating

Question

Please run this code. You will see when you click on a row in the datatable the number from the "a" column is plotted. That's done using callback and observeEvent. That works fine.

library(shiny)
library(DT)
runApp(shinyApp(
  ui = fluidPage(
                   DT::dataTableOutput('table')  ,
                   selectInput("NUMBER", "Number:", c(1,100,1000000),selected = 1),
                   plotOutput("p")
                   ),
  server = function(input, output, session) {

    NUMBER = reactive({
      input$NUMBER
    })

    output$table <- DT::renderDataTable({
      datatable(data.frame(a = c(85,7),b=c(444,2)), rownames = FALSE, selection = 'none', callback=

      JS("table.on('click.dt', 'tr', function() {
           var data=table.row(this).data();
           Shiny.onInputChange('rows',data[0]);
          });")
      )}
    )

    observeEvent(input$rows, {

      print( input$rows)   
      print( class( input$rows)  )
      a = as.numeric(input$rows)

      print(a)
      print(NUMBER())
      new_number = a      #THIS WORKS!!!
      #new_number = a  * as.numeric(NUMBER())    #THIS DOES NOT WORK     multiple a by the number in the slider when the SLIDER Is CHANGED

      output$p = renderPlot({

        # browser()
        plot( new_number )
      })

    })}
))

But you also see a "NUMBER" slider input. When the user changes the slider I would like the plot to update so that the plot shows a times the number selected in the slider. So:

comment out this line:

new_number = a 

and uncomment this line:

new_number = a  * as.numeric(NUMBER()) 

Now rerun the code and you will see that as you select different numbers from the slider but nothing happens. This is because

new_number = a  * as.numeric(NUMBER()) 

is inside the ObserveEvent function and the table WAS NOT clicked...just the slider was changed. So how NUMBER() be made available so that this works?

Thank you.

Answer 1

All you had to do is put an observeEvent into your observeEvent :) That way when rendering a new plot R grabs the updated input. Hope this helps !

 library(shiny)
    library(DT)

    runApp(shinyApp(

  ui = fluidPage(
    DT::dataTableOutput('table')  ,
    selectInput("NUMBER", "Number:", c(1,100,1000000), selected = 1),
    plotOutput("p")
  ),

  server = function(input, output, session) {

    NUMBER = reactive({
      input$NUMBER
    })

    output$table <- DT::renderDataTable({
      datatable(data.frame(a = c(85,7),b=c(444,2)), rownames = FALSE, selection = 'none', callback=

                  JS("table.on('click.dt', 'tr', function() {
                     var data=table.row(this).data();
                     Shiny.onInputChange('rows',data[0]);
    });")
      )}
      )

    observeEvent(input$rows, {

      print( input$rows)   
      print( class( input$rows)  )
      a = as.numeric(input$rows)
      new_number <- a

      observeEvent(input$NUMBER, {

        print(a)
        print(NUMBER())

        number = a  * as.numeric(NUMBER())    

        output$p = renderPlot({

          # browser()
          plot( number )
        })

      })

      output$p = renderPlot({

        # browser()
        plot( new_number )

      })

    })

    }
   ))