mages' blog

Interactive HTML presentation with R, googleVis, knitr, pandoc and slidy

Tonight I will give a talk at the Cambridge R user group about googleVis. Following my good experience with knitr and RStudio to create interactive reports, I thought that I should try to create the slides in the same way as well.

Christopher Gandrud's recent post reminded me of deck.js, a JavaScript library for interactive html slides, which I have used in the past, but as Christopher experienced, it is currently not that straightforward to use with R and knitr.

Thus, I decided to try slidy in combination with knitr and pandoc. And it worked nicely.

I used RStudio again to edit my Rmd-file and knitr to generate the Markdown md-file output. Following this I run pandoc on the command line to convert the md-file into a single slidy html-file:

pandoc -s -S -i -t slidy --mathjax Cambridge_R_googleVis_with_knitr_and_RStudio_May_2012.md -o Cambridge_R_googleVis_with_knitr_and_RStudio_May_2012.html

Et volià, here is the result:

Addition (2 June 2012)

Oh boy, knitr and Markdown are hitting a nail. With slidify by Ramnath Vaidyanathan another project sprung up to ease the creation of web presentations.

End User Computing and why R can help meeting Solvency II

John D. Cook gave a great talk about 'Why and how people use R'. The talk resonated with me and highlighted why R is such a great tool for end user computing. A topic which has become increasingly important in the European insurance industry.

John's main point on why people use R is that R gets the job done and I think he is spot on. Of course that's the trouble with R sometimes as well, or to quote Bo again:

"The best thing about R is that it was developed by statisticians.
"The worst thing about R is that it was developed by statisticians."
Bo Cowgill, Google

Interactive reports in R with knitr and RStudio

Last Saturday I met the guys from RStudio at the R in Finance conference in Chicago. I was curious to find out what RStudio could offer. In the past I have used mostly Emacs + ESS for editing R files. Well, and what a surprise it was. JJ, Joe and Josh showed me a preview of version 0.96 of their software, which adds a close integration of Sweave and knitr to RStudio, helping to create dynamic web reports with the new R Markdown and R HTML formats more easily.

Screen shot of RStudio with a knitr file (*.Rmd) in the top left window. Notice also the integrated knitr button.

You probably have come across Sweave in the past, but knitr is a fairly new package by Yihui Xie that brings literate programming to a new level. In particular the markdown approach allows me to create web content really quickly, without worrying to much about layout and R formatting. I begin to wonder if PDF and paper will be replaced by tablets and HTML5 in the future.

Here is a simple example. The knitr source code is available on Github.

Waterfall charts in style of The Economist with R

Waterfall charts are sometimes quite helpful to illustrate the various moving parts in financial data, in particular when I have positive and negative values like a profit and loss statement (P&L). However, they can be a bit of a pain to produce in Excel. Not so in R, thanks to the waterfall package by James Howard. In combination with the latticeExtra package it is nearly a one-liner to produce a good looking waterfall chart that mimics the look of The Economist:

Example of a waterfall chart in R

library(latticeExtra)
library(waterfall)
data(rasiel) # Example data of the waterfall package
rasiel
#    label          value   subtotal
# 1  Net Sales       150    EBIT
# 2  Expenses       -170    EBIT 
# 3  Interest         18    Net Income
# 4  Gains            10    Net Income
# 5  Taxes            -2    Net Income

asTheEconomist(
               waterfallchart(value ~ label, data=rasiel,
                              groups=subtotal, main="P&L")
               )

Of course you can create a waterfall chart also with ggplot2, the Learning R blog has a post on this topic.

Next Kölner R User Meeting: 6 July 2012

The next Cologne R user group meeting is scheduled for 6 July 2012. All details are available on the new KölnRUG Meetup site. Please sign up if you would like to come along, and notice that there is also pub poll for the after "work" drinks. Notes from the first Cologne R user group meeting are available here.