Access/use R console when running a shiny app

Question

Does anybody know if one is able to access the R console when running a shiny app? (running the shiny application in background would also be helpful, if that\'s possible)

Answer 1

R (and shiny) run single-threaded. This thread is used by the shiny application so you cannot interact with R whenever the app is running. If you want to run interactive commands during a shiny session you need to put a browser() inside your application like mentioned by @eric-canton.

A very simple application could look like this

library(shiny)

d <- data.frame(1:10, 1:10)

ui <-  fluidPage(
  actionButton("browser", "Trigger browser()"),
  actionButton("reload", "Reload Plot"),
  plotOutput("plot")
)


server <- function(input, output, session) {
  observeEvent(input$browser, {
    browser()
    1 + 1
  })

  output$plot <- renderPlot({
    input$reload
    plot(d)
  })
}

shinyApp(server = server, ui = ui)

Some comments about the code

• I put 1 + 1 after the browser() command because setting browser() as the last argument tends to stop the interactive terminal unexpectedly in my experience
• You need some shiny event to trigger the redrawing of the plot, because d is not a reactive value
• If you are on the console you need to assign a new value to d by using the <<- operator because d lives outside the function you are calling:

Browse[2]> d <<- data.frame(x = 1:200, y = 200:1)

• You can jump out of interactive console and resume the app by entering c and hitting Enter