Shiny: Overview
Shiny is an open package from RStudio.
It provides a web application framework to create interactive web applications (visualization) called “Shiny apps”.
It can be found at https://shiny.rstudio.com/
What is so special about Shiny?
It allows R users:
to build and share highly interactive web-enabled applications without having to invest significant among of time and efforts to master core web design technologies such as html5, Javascript and CSS.
to integrate the analytical and visualisation packages of R without having to change from one programming language to another.
The Structure of a Shiny app
A Shiny app comprises of two components, namely:
user-interface script, and
server script.
Shiny’s user-interface, ui.R
The ui.R script controls the layout and appearance of a shiny app.
It is defined in a source script name ui.R.
Actually, ui is a web document that the user gets to see, it is based on the famous Twitter bootstrap framework, which makes the look and layout highly customizable and fully responsive.
In fact, you only need to know R and how to use the shiny package to build a pretty web application. Also, a little knowledge of HTML, CSS, and JavaScript may help.
Shiny’s server server.R
The server.R script contains the instructions that your computer needs to build your Shiny app.
You are expected to:
know how to program with R.
familiar with Tidyverse, specifically dplyr, tidyr and ggplot2
Building a Shiny app
A Shiny app can be in a form of a single file called app.R.
Alternatively, a Shiny app can be also created using separate ui.R and server.R files.
The separate files way is preferred when the app is complex and involves more codes.
Shiny app example
The preview of Shiny app can be seen below:
The app reads the Exam_data.csv and generate a histogram. The user can select the subject to be displayed, the number of bins for the histogram, and enable/disable the data table. In this simple Shiny app, we were able to load the dataset, work with titlePanel, sidebarLayout(), checkboxInput(), plotOutput(), dataTableOutput(), renderPlot(), and renderDataTable().
Shiny app code
The code chunk can be seen below:
library(shiny)
library(tidyverse)
exam <- read_csv("data/Exam_data.csv")
# Define UI for application
ui <- fluidPage(
titlePanel("Pupils Examination Results Dashboard"),
sidebarLayout(
sidebarPanel(
selectInput(inputId = "variable",
label = "Subject: ",
choices = c("English" = "ENGLISH",
"Maths" = "MATHS",
"Science" = "SCIENCE"),
selected = "ENGLISH"),
sliderInput(inputId = "bin",
label = "Number of bins",
min = 5,
max = 20,
value = c(10)),
checkboxInput(input = "show_data",
label = "Show data table",
value = TRUE)
),
mainPanel(
plotOutput("distPlot"),
DT::dataTableOutput(outputId = "examtable")
)
)
)
# Define server logic required
server <- function(input, output) {
output$distPlot <- renderPlot({
#unlist - data contains string
x <- unlist(exam[,input$variable])
ggplot(exam, aes(x)) +
geom_histogram(bins = input$bin,
color = "black",
fill = "light blue")
})
output$examtable <- DT::renderDataTable({
if (input$show_data){
DT::datatable(data = exam %>%
select(1:7),
options = list(pageLength = 10),
rownames = FALSE)
}
})
}
# Run the application
shinyApp(ui = ui, server = server)
Reference