lr.js

<script src="https://github.com/livereload/livereload-js/raw/master/dist/livereload.js?host=localhost"></script>

sage.js

<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<script src="http://aleph.sagemath.org/static/jquery.min.js"></script>
<script src="http://aleph.sagemath.org/static/embedded_sagecell.js"></script>
<script>
$(function () {
    sagecell.makeSagecell({inputLocation: 'div.compute-r',
                           evalButtonText: 'Evaluate',
                           defaultLanguage: "r", 
                           languages: sagecell.allLanguages});
});
</script>
<div class="compute-r"><script type="text/x-sage">
x <- 3; x <- x + 3
print(x)
</script></div>

server.R

library(shiny)

	shinyServer(function(input, output) {

	output$Routput=reactivePrint(function(){
		cat(input$code,"\n")
		eval(parse(text = input$code))
	})
})

ui.R

library(shiny)

shinyUI(pageWithSidebar(

  headerPanel("Basic notebook"),

  sidebarPanel(helpText("Include button to add input and output fields")),

  mainPanel(
    includeHTML('lr.js'), # needed for livereload
    tabsetPanel(id = "tabs",
	    tabPanel("Notebook",textInput("code","Input R-code", value = 'x <- 3; x <- x + 3'), verbatimTextOutput("Routput"), helpText("Add button to evaluate the code and make the return panel conditional on the the type of output (e.g., text, plot, table).")),
		tabPanel("Sage", includeHTML('sage.js'))
	)
  )
))