Book Image

Web Application Development with R Using Shiny - Third Edition

By : Chris Beeley, Shitalkumar R. Sukhdeve
Book Image

Web Application Development with R Using Shiny - Third Edition

By: Chris Beeley, Shitalkumar R. Sukhdeve

Overview of this book

Web Application Development with R Using Shiny helps you become familiar with the complete R Shiny package. The book starts with a quick overview of R and its fundamentals, followed by an exploration of the fundamentals of Shiny and some of the things that it can help you do. You’ll learn about the wide range of widgets and functions within Shiny and how they fit together to make an attractive and easy to use application. Once you have understood the basics, you'll move on to studying more advanced UI features, including how to style apps in detail using the Bootstrap framework or and Shiny's inbuilt layout functions. You'll learn about enhancing Shiny with JavaScript, ranging from adding simple interactivity with JavaScript right through to using JavaScript to enhance the reactivity between your app and the UI. You'll learn more advanced Shiny features of Shiny, such as uploading and downloading data and reports, as well as how to interact with tables and link reactive outputs. Lastly, you'll learn how to deploy Shiny applications over the internet, as well as and how to handle storage and data persistence within Shiny applications, including the use of relational databases. By the end of this book, you'll be ready to create responsive, interactive web applications using the complete R (v 3.4) Shiny (1.1.0) suite.
Table of Contents (11 chapters)

Handling errors (including validate() and req())

Are you getting an error message in red on your screen? Are you or your user able to understand that message? The answers to such questions can be validation errors using validate() and req().

Validate

This is designed to lead the user through the UI of the Shiny app. Imagine that we have a situation where we need to plot a graph based on some values of a list box and it throws up a red message. This looks stressful to the user. We need to provide a precautionary message to make sure the reader enters a valid input. validate is a way of checking the input and providing a message, using need. In the following code, we can see that validate is checking for a phone number. If the...