Shiny Package in R Programming

The package is an appropriate way to organize the work and share it with others. Packages in the R Programming language are a collection of R functions, compiled code, and sample data. They are stored under a directory called “library” in the R environment. By default, R installs a set of packages during installation. One of the most important packages in R is the Shiny package. Shiny is an R package that makes it easy to build interactive web apps straight from R.

Shiny package Install in R language

To use a package in R programming one must have to install the package first. This task can be done using the command install.packages(“packagename”). To install the whole Shiny package type this.

To install the latest development builds directly from GitHub, run this instead.

Important Verb Functions in Shiny Package R Language

fluidPage(): It creates a page with a fluid layout. A fluid page layout consists of rows which in turn include columns. Rows exist for the purpose of making sure their elements appear on the same line and columns exist for the purpose of defining how much horizontal space within a 12-unit wide grid. Fluid pages scale their components in real-time to fill all available browser width.

Syntax:

   fluidPage(..., title = NULL, theme = NULL)

Parameter	Description
...	Elements to include within the page.
title	The browser window title.
theme	Alternative Bootstrap stylesheet.

Example:

This is a basic shiny app template. 

Output:

👁 FluidPage

shinyApp(): It creates Shiny app objects from either an explicit UI/server pair or bypassing the path of a directory that contains a Shiny app.

Syntax:

   shinyApp(ui, server, onStart = NULL, options = list(), uiPattern = "/", enableBookmarking = NULL)

   shinyAppDir(appDir, options = list())

   shinyAppFile(appFile, options = list())</p 

Parameter	Description
ui	The UI definition of the app.
server	It has three parameters: input, output, and session. It is called once for each session to ensure that each app is independent.
onStart	A function that will be called before the app is actually run.
options	Options that should be passed to the runApp.
uipattern	A regular expression that will be applied to each  GET request to determine whether the ui should be used to handle the request.
enableBookmarking	Can be "url", "server", or "disable".The default value is NULL.
appDir	Path to directory that contains a Shiny app.
appFile	Path to a .R file containing a Shiny application.

Output:

👁 shinyApp

• Library Import: The code begins by importing the shiny package using the library(shiny) function. Shiny is an R package for creating interactive web applications.
• UI Definition: The ui variable is defined to create a Shiny app's user interface (UI). It includes a slider input (sliderInput) allowing the user to choose a number between 1 and 1000 and a placeholder for a plot (plotOutput("hist")).
• Server Logic: The server function is defined to specify the server-side logic. It includes a reactive expression (renderPlot) that generates a histogram using hist() based on a random normal distribution with a sample size determined by the user's slider input (input$num).
• App Initialization: The Shiny app object is created using shinyApp(ui = ui, server = server), combining the UI and server components.
• App Execution: The Shiny app is executed, and the interactive web application is launched. Users can interact with the slider to choose a number, and the corresponding histogram is dynamically updated based on the selected sample size.

reactive(): It creates a reactive expression. A reactive expression is an expression whose result will change over time.reactive() wraps a normal expression to create a reactive expression.

Syntax: reactive(x, env = parent.frame(), quoted = FALSE, label = NULL)

Parameter	Description
x	An expression.
env	The parent environment for reactive expression.
quoted	Is the expression quoted? By default, this is FALSE.  This is useful when you want to use an expression that is stored in a variable
label	A label for reactive expression.

Output:

👁 reactive_50

Now, change the input value from 50 to 100 to see what happens.

👁 reactive_100

The output values(histogram and summary) also change with the alternation in the input values, i.e the app has reactivity.

observeEvent(): It triggers code to run on servers. Respond to "event-like" reactive inputs, values, and expressions.

Syntax:

observeEvent(eventExpr, handlerExpr, event.env = parent.frame(), event.quoted = FALSE, handler.env = parent.frame(), handler.quoted = FALSE, label = NULL, suspended = FALSE, priority = 0, domain = getDefaultReactiveDomain(), autoDestroy = TRUE, ignoreNULL = TRUE, ignoreInit = FALSE, once = FALSE)

Parameter	Description
eventExpr	A expression that represents the event.It can be  a simple or a complex reactive expression.
handler.Expr	The expression to call whenever eventExpr is invalidated.
event.env	The parent environment for eventExpr.  By default, this is the calling environment.
event.quoted	Returns whether the eventExpr expression is quoted or not.  By default, this is FALSE.
handler.env	The parent environment for handlerExpr. By default, this is the calling environment.
handler.quoted	Returns whether the handlerExpr expression is quoted or not.  By default, this is FALSE.
label	A label for the observer or reactive
suspended	If TRUE, start the observer in a suspended state.
priority	An integer or numeric that controls the priority  with which this observer should be executed.Positive,Negative and Zero values are allowed.
autodestroy	If TRUE (the default), the observer will be automatically  destroyed when its domain (if any) ends.
ignoreNULL	Whether the action should be triggered when the input is NULL.
ignoreInit	If TRUE, then, when this observeEvent is first created/initialized, ignore the handlerExpr (the second argument), whether  it is otherwise supposed to run or not. The default is FALSE.
once	Whether this observeEvent should be immediately destroyed after  the first time that the code in handlerExpr is run.

Output:

👁 observeEvent
👁 observeEvent

eventReactive(): A reactive expression that only responds to specific values. Respond to "event-like" reactive inputs, values, and expressions.

Syntax:

eventReactive(eventExpr, 
valueExpr, 
event.env = parent.frame(), 
event.quoted = FALSE, 
value.env = parent.frame(), 
value.quoted = FALSE, 
label = NULL, 
domain = getDefaultReactiveDomain(), 
ignoreNULL = TRUE, 
ignoreInit = FALSE)

Parameter	Description
eventExpr	An expression that represents the event.It can be a simple or a complex reactive expression.
valueExpr	It produces the return value of the eventReactive. It will be executed within an isolate() scope.
event.env	The parent environment for eventExpr. By default, this is the calling environment.
event.quoted	Returns whether the eventExpr expression is quoted or not. By default, this is FALSE.
value.env	The parent environment for valueExpr. By default, this is the calling environment.
value.quoted	Returns whether the valueExpr expression is quoted or not. By default, this is FALSE.
ignoreNULL	Whether the action should be triggered when the input is NULL.
ignoreInit	If TRUE, then, when this observeEvent is first created/initialized,  ignore the handlerExpr (the second argument), whether  it is otherwise supposed to run or not. The default is FALSE.

Output:

👁 eventReactive

Here, the output does not change with the input values until and unless the update button is triggered

👁 eventReactive

actionButton(): It creates an action button or a link. Their initial value is zero, and increments by one each time it is pressed.

Syntax:

   actionButton(inputId, label, icon = NULL, width = NULL, ...)

   actionLink(inputId, label, icon = NULL, ...)

Parameter	Description
inputId	The input slot that will be used to access the value.
label	The contents of the button or link.
icon	An optional icon() to appear on the button.
width	The width of the input(ex-'200px',or'100%').
....	Named attributes to be applied to the button or link.

Output:

👁 actionButton

The output gets updated as soon as the actionButton(Go!) is clicked.

👁 actionButton

checkboxGroupInput(): It creates a group of checkboxes that can be used to toggle multiple choices independently. The server will receive the input as a character vector of the selected values.

Syntax:

checkboxGroupInput(inputId, label, choices = NULL, selected = NULL, inline = FALSE, width = NULL, choiceNames = NULL, choiceValues = NULL)

Parameter	Description
inputId	The input slot that will be used to access the value.
label	The contents of the button or link.
choices	List of values to show checkboxes for. If elements of  the list are named then that name rather than the value is displayed to the user.
selected	The initial selection.
inline	If TRUE, render the choices horizontally.
width	The width of the input(ex-'200px',or'100%').
choiceValues, choiceNames	List of names and values.

Output:

👁 checkboxGroupInput

textInput(): It creates a text input label.

Syntax:

   textInput(inputId, label, value = "", width = NULL, placeholder = NULL)

Parameter	Description
inputId	The input slot that will be used to access the value.
label	The contents of the button or link.
value	The initial value.
width	The width of the input(ex-'200px',or'100%').
placeholder	A character string giving the user a hint as to what can be entered into the control.

Output:

👁 textInput

textOutput(): It creates a text output element. Render a reactive output variable as text within an application page.

Syntax:

   textOutput(outputId, container = if (inline) span else div, inline = FALSE)

Parameter	Description
outputId	The output variable to read the value from.
container	A function to generate an HTML element to contain the text.
inline	Use an inline (span()) or block container (div()) for the output.

Output:

👁 textOutput

wellPanel(): Creates a panel with a slightly inset border and gray background.

Syntax: wellPanel(...)

Parameter	Description
...	UI elements to include inside the panel.

Output:

👁 wellPanel

Observe that the histogram lies inside a gray-colored box(wellPanel).

This all function we can apply on different types of plots also now we apply this on scatter plot.

Output:

👁 Screenshot-(5)

Shiny package helps to host standalone apps on a webpage embed them in R Markdown documents or build dashboards. One can also extend Shiny apps with CSS themes, HTML widgets, and JavaScript actions.