Building Shiny APP using R

Introduction

Shiny is a new package from RStudio that can be used to build interactive web application straight from R. It may be sound so much surprisingly for R users who have no experience in web development. Even you can build useful web application with only few lines of code. You don’t need to know any HTML/CSS/JavaScript. Shiny package provides fast bidirectional communication between the web browser and R using the websockets package. Even you can also use HTML, CSS and JavaScript in your Shiny code for more flexibility. In fact you can do quite a lot with shiny: like display R Objects, tables, Plots or anything else you do in R. To get more information about shiny, you can visit Shiny Tutorial website.

This tutorial is a hands-on activity for learning how to build shiny apps. And how to include yoy R code in shiny app. 

Installation

Install.packages(“shiny”)

To ensure you successfully installed Shiny, try running one of the demo apps.

library(shiny)

runExample(‘01_hello’) 

Structure of a Shiny App

Shiny app have two components

        1. A user-interface script

        2.  A server script

The user-interface (ui) script controls the layout and appearance of your app. It is a source file named ui.R. While server.R script contains the instructions that your computer needs to build your app

To start shiny app, go to File-> New File Name -> Shiny Web app. It will give you two options.

First options is Single File, in this options only single file is created where you write your shiny code. In second options you will get two file ui.R and server.R.

If you selecting multiple File options. You will see by default example is already programmed in both scripts. Now we will see how to use Rscript code in shiny app. 

Create Box Plot using Shiny App

ui.R

library(shiny) head(iris) # Define UI for application that draws a histogram shinyUI(fluidPage(     # Application title   titlePanel("Iris"),     # Sidebar with a slider input for the number of bins   sidebarLayout(     sidebarPanel(      h1("Boxplot of Iris Species")      ),         # Show a plot of the generated distribution     mainPanel(       plotOutput("myplot")     )   ) ))

server.R

library(shiny) library(ggplot2) shinyServer(function(input, output) {   output$myplot <- renderPlot({     p <- ggplot(data =iris, aes(x=Species,y=Sepal.Length, colors=factor(Species)))  graph <- p+geom_boxplot(fill=heat.colors(3))  print(graph)       }) })

After saving the file, RStudio should recognize the shiny app, you should see the usual Run button at the top change to Run App.

If you don’t see the Run button, it means you either have very old version of RStudio, don’t have shiny installed. Click on Run button, and now your app should run.

Output:

You should see that console has some text printed in the form of listening on http://127.0.0.1: 3504. You will also notice that you cannot run any commands in the console. This is because R is busy-your R sessions is currently powering Shiny app and listening for user interface.

To stop the application, click on stop button and also you can press Escape button.

This is a simple way to encode R code in shiny App. Similarly you can do lots of things which you do in R. you can also plot Data Frame and so on. If you want to learn more   about this package go to Shiny Tutorial website.