shiny app example

app.R

shinyApp(
	ui = navbarPage(title="test", id="mainNavbarPage",
		
		tabPanel("Input", value="tabinput",
			numericInput('n', 'Number of obs', 100),
			actionButton(inputId="submit_button", label="Submit")
		),

		tabPanel("Output", value="taboutput",
			verbatimTextOutput("messages"),
			plotOutput('plot')
		)
	),
	server = function(input, output, session) {

		messages <- ""

		observeEvent(input$submit_button, {
			
			# Move to results page first
			updateNavbarPage(session, "mainNavbarPage", selected="taboutput")

			messages <- paste(messages, "Welcome to the app!\n")
			# Tell user what is happening
			output$messages <- renderPrint({
				cat(messages)
			})

			# Perform lots of calculations that may take some time

			messages <- paste(messages, "Sleeping for no reason...\n")
			output$messages <- renderPrint({
				cat(messages)
			})
			Sys.sleep(5)

			messages <- paste(messages, "Creating plot...\n")
			output$messages <- renderPrint({
				cat(messages)
			})

			output$plot <- renderPlot({ hist(runif(input$n)) })

			messages <- paste(messages, "Complete!\n")
			output$messages <- renderPrint({
				cat(messages)
			})
		})
	}
)