Update data in shiny application without refreshing the whole application

Question

I have an application for real time data visualization build with R shiny library. I do periodic data reload from file using reactivePoll function. What I do not like about this is that whenever data reloads the whole application refreshes.

So for example if I have DT table output with selection and I use this selection input$table_rows_selected it resets to NULL whenever data reloads which is not user-friendly at all.

Is it overall possible to change data output without interrupting user?

UPDATE.

Can this be achieved with any other package for displaying tables - googleVis or other?

Working example.

library(shiny)
library(DT)

runApp(shinyApp(
  ui = fluidPage(dataTableOutput('table')),
  server = function(input, output, session) {
    pollData <- reactivePoll(4000, session,
                             checkFunc = function(){ Sys.time() },
                             valueFunc = function(){ data.frame(id = sample(letters[1:3]), a = runif(3), b = runif(3), c = runif(3)) })
    output$table <- renderDataTable({pollData()})
    proxy <- dataTableProxy('table')
    observeEvent(pollData(), {
      selectRows(proxy, input$table_rows_selected)
    })}
))

I have taken this example from @NicE answer and added id column. The point is that @NicE answer is OK if one needs certain row to be selected when that row is identified by the row number.

Now suppose I need a row to be selected when that row is identified by some id value. That is if I select a row with id equal b, then the next time data reloads I want the row to be selected with the same id value.

Answer 1

You could use a dataTableProxy to select rows when the datable is created after a pollData update. Here's an example, the dataframe is refreshed every 4 seconds:

library(shiny)
library(DT)

ui <- fluidPage(dataTableOutput("table"))

server <- function(input,output,session){
        values <- reactiveValues()
        pollData <- reactivePoll(4000, session,
                                 checkFunc=function(){
                                         Sys.time()
                                 },
                                 valueFunc=function(){                             
                                         data.frame(a=sample(c("a","b","c"),3),b=runif(3),c=runif(3),stringsAsFactors = F)
                                 })

        output$table <- renderDataTable({ pollData()})

        observe({
                values$selected <- pollData()$a[input$table_rows_selected]
        })

        proxy = dataTableProxy('table')
        observeEvent(pollData(),{
                selectRows(proxy, which(pollData()$a %in% values$selected))
        })
}

shinyApp(ui,server)

Update: on the above code, when the data changes, the selected rows are the ones that have the same first column as previously.