Interactive Documents

Slidify + Shiny

View the Project on GitHub slidify/interactive

Interactive Documents with R

I gave a talk recently at the NY Open Statistical Programming Meetup, on how to use R to generate documents which are dynamic and interactive. I thought it would be useful to capture the main idea of the talk with a short demo. You can either watch the screencast, view the resulting document or read along for more information.


Getting Started

You will need to install development versions of many R packages in order to replicate the steps in this tutorial. This will require you to upgrade to R 3.0 if you have not already done so.

require(devtools)
install_github(c('slidify', 'slidifyLibraries'), 'ramnathv', ref = 'dev')
install_github('rCharts', 'ramnathv')
install_github('shiny', 'rstudio')

Create Document

Now that you have all the required packages installed, we will begin by creating a document. The easiest way to do this is to use the author function that comes with slidify.

author('interactive')

This will create a folder called interactive in your working directory, populate it with a skeleton, and open index.Rmd. We will start by first editing the YAML front matter, adding title, subtitle, author and job.

---
title       : Interactive Documents with R
subtitle    : Slidify + Shiny
author      : Ramnath Vaidyanathan
job         : R Hacker
framework   : io2012        # {io2012, html5slides, shower, dzslides, ...}
highlighter : highlight.js  # {highlight.js, prettify, highlight}
hitheme     : tomorrow      # 
widgets     : []            # {mathjax, quiz, bootstrap}
mode        : selfcontained # {standalone, draft}
---

Inject Interactivity

There are several ways of injecting interactivity into an R Markdown document, and I will illustrate a few methods.

Interactive Quiz

Let us start by creating a quiz question, the usual way we do. 

---
## Question 1

What is 1 + 1?

1. 1
2. 2
3. 3
4. 4

hint

This is a hint

explanation

This is an explanation

There is nothing different so far, and if you slidify the document at this stage, you will just see a regular question with no interactivity. Now, to make this question interactive, we need to add some properties to the document.

First, we need to add the quiz widget and the bootstrap widget to the YAML front matter. This will allow the document to take advantage of the interactivity provided by the quiz widget, and the styling provided by the bootstrap widget.

widgets    : [bootstrap, quiz]

Second, we need to add some markup to the slide that will allow slidify to transform it into an interactive question.

--- &radio
## Question 1

What is 1 + 1?

1. 1
2. _2_
3. 3
4. 4

*** .hint
This is a hint

*** .explanation
This is an explanation

There are three components to the markup we add on this slide.

  1. The &radio added to the slide separator instructs slidify to use the radio template, which ships with the quiz widget.
  2. The answer is marked up by enclosing it within underscores.
  3. The hint and the explanation are preceded by three stars and a dot, which instruct slidify to parse them as blocks, that will be made use of by the radio layout.

If you slidify the document at this stage, you should see a quiz question that looks like this.

Try selecting an answer and submitting it, or asking for a hint. You will see that Slidify has utilized the markup properties and the content to create an interactive quiz question. In addition to the radio layout, the quiz widget supports seven other types of questions. I will post a full featured example on the quiz widget later.

Interactive Chart

We will now add an interactive chart to the document using the package rCharts, and the javascript charting library nvd3. As before, we first need to add nvd3 as a widget in the YAML front matter. However, since nvd3 does not ship with slidifyLibraries, we will add it as an external widget.

ext_widgets: {rCharts: [libraries/nvd3]}

We now add the slide with a knitr code chunk that creates the plot.

---
## Interactive Chart

``{r echo = F, results = 'asis'}
require(rCharts)
haireye = as.data.frame(HairEyeColor)
n1 <- nPlot(Freq ~ Hair, group = 'Eye', type = 'multiBarChart',
  data = subset(haireye, Sex == 'Male')
)
n1$print('chart1')
```

Run slidify on the document, and you will see an interactive NVD3 plot with some nice controls.

Interactive Console

Next, we will add an interactive console to our document. It allows the user to execute R code right inside the document, and see the resulting output. This is a very useful feature for pedagogical purposes, where you want to provide executable examples right inside a tutorial. Adding an interactive console is even easier than the quiz.

As before, we first add the shiny and interactive widgets to the list of widgets in the YAML front matter.

widgets    : [bootstrap, quiz, shiny, interactive]

We markup the slide and a knitr code chunk to instruct slidify to treat it as an interactive code chunk.

--- &interactive
## Interactive Console

``{r opts.label = 'interactive', results = 'asis'}
require(googleVis)
M1 <- gvisMotionChart(Fruits, idvar = 'Fruit', timevar = 'Year')
print(M1, tag = 'chart')
```

That is it, we are done! Ah, one more thing remains. You can no longer use the slidify function, since we need this document to be run using a shiny server. Slidify ships with a runDeck function that takes care of all the boilerplate for you. Just make sure that you are in the same directory as the Rmd file and then do runDeck(). This will open the document as a Shiny application, and if you navigate to the new slide, you will see an interactive console as shown below. Clicking on the run button will execute the code and you will see a nice and shiny googleVis motionchart on the right! Neat right!!

Interactive Chart with Controls

Finally, we will use Shiny to add interactive controls to the chart we created previously. Suppose that we want to control Sex and the type of plot. Let us first add the UI. slidifyUI behaves almost like shinyUI except that it outputs a character vector.

```{r opts.label = 'shiny'}
slidifyUI(
  sidebarPanel(
    selectInput('sex', 'Choose Sex', c('Male', 'Female')),
    selectInput('type', 'Choose Type',
      c('multiBarChart', 'multiBarHorizontalChart')
    )
  ),
  mainPanel(
    tags$div(id = 'nvd3plot', class='shiny-html-output nvd3 rChart')
  )
)
`` `

We now need to add a plotting function to the server side. runDeck is set up so that any R file in the apps directory that starts with app will be automatically sourced into shinyServer. Hence, let us create an apps directory and add the following code the app1.R.

Note that the code is almost identical to what we used previously, except that now the Sex and type of chart are not hardcoded, and instead being controlled by the UI.

require(rCharts)
output$nvd3plot <- renderChart({
  haireye = as.data.frame(HairEyeColor)
  n1 <- nPlot(Freq ~ Hair, group = 'Eye', type = input$type,
    data = subset(haireye, Sex == input$sex)
  )
  n1$set(dom = 'nvd3plot', width = 600)
  n1
})

If you use runDeck(), you will be able to see a nice nvd3plot that can be controlled using the sidebar. The final interactive document can be found in the folder named idocs. You can download the repo and run runDeck("idocs") to view it on your local machine.