Deploying and updating front end database applications
It’s simple to create reactive expression: just pass a normal expression into value changes.Now that we’ve taken a deeper look at some of the core concepts, let’s revisit the source code and try to understand what’s going on in more depth.The next section focuses on the mechanics of building a Shiny application from the ground up and also covers tips on how to run and debug Shiny applications.Let’s walk through the steps of building a simple Shiny application.The Shiny web framework is fundamentally about making it easy to wire up Since Shiny web apps are interactive, the input values can change at any time, and the output values need to be updated immediately to reflect those changes.Shiny comes with a reactive programming library that you will use to structure your application logic.The application will be called “Miles Per Gallon” so we specify that as the title when we create the header panel. We’ve now created the most minimal possible Shiny application.You can run the application by calling the If everything is working correctly you’ll see the application appear in your browser looking something like this: We now have a running Shiny application however it doesn’t do much yet.
The application we’ll be building uses the mtcars data from the R datasets package, and allows users to see a box-plot that explores the relationship between miles-per-gallon (MPG) and three other variables (Cylinders, Transmission, and Gears).
What’s interesting about reactive expressions is that whenever they execute, they automatically keep track of what reactive values they read and what reactive expressions they invoked.