Dynamic Data Visualizations in the Browser Using Shiny
After being busy the last two weeks teaching and attending academic conferences, I finally found some time to do what I love, program data visualizations using R. After being interested in Shiny for a while, I finally decided to pull the trigger and build my first Shiny app!
I wanted to make a proof of concept app which contained the following dynamics which are the basics of any UI design:
1) dynamic UI options
2) dynamically updated plot based on UI inputs
Here is what I came up with.
The app consists of a user interface (UI) for selecting the data, variable to plot , grouping factor for colors and four plotting options: boxplot (above), histogram, density plot and bar graph. As an added bonus the user can select to show or hide jittered points in the boxplot visualization.
Generally #2 above was well described and easy to implement, but it took a lot of trial and error to figure out how to implement #1. Basically to generate dynamic UI objects, the UI objects need to be called using the function shiny:::uiOutput() in the ui.R file and their arguments set in the server.R file using the function shiny:::renderUI(). After getting this to work everything else fell in place.
Having some experience with making UI’s in VBA (visual basic) and gWidgets; Shiny is a joy to work with once you understand some of its inner workings. One aspect I felt which made the learning experience frustrating was the lack of informative errors coming from Shiny functions. Even using all the R debugging tools having Shiny constantly tell me something was not correctly called from a reactive environment or the error was in the runApp() did not really help. My advice to anyone learning Shiny is to take a look at the tutorials, and particularly the section on Dynamic UI. Then pick a small example to reverse engineer. Don’t start off too complicated else you will have a hard time understanding which sections of code are not working as expected.
Finally here are some screen shots, and keep an eye out for more advanced shiny apps in the near future.