R编程中的闪亮包

包是组织工作并与他人共享的适当方式。 R 编程语言中的包是 R 函数、编译代码和示例数据的集合。它们存储在 R 环境中名为“库”的目录下。默认情况下，R 在安装过程中会安装一组包。 R 中最重要的包之一是Shiny包。 Shiny是一个 R 包，可以轻松地直接从 R 构建交互式 Web 应用程序。它有助于在网页上托管独立应用程序或将它们嵌入 R Markdown 文档或构建仪表板。还可以使用 CSS 主题、htmlwidget 和 JavaScript 操作来扩展 Shiny 应用程序。

闪亮的包安装在R语言

要在 R 编程中使用包，必须首先安装包。可以使用命令install.packages(“packagename”)完成此任务。要安装整个Shiny包，请输入：

install.packages("shiny")

要直接从 GitHub 安装最新的开发版本，请运行以下命令：

if (!require("remotes"))
  install.packages("remotes")
remotes::install_github("rstudio/shiny")

R 语言示例中的闪亮包

Shiny 包中的重要动词函数

• fluidPage()：它创建一个具有流体布局的页面。流畅的页面布局由行组成，而行又包括列。行的存在是为了确保它们的元素出现在同一行上，而列的存在是为了定义 12 单位宽的网格中的水平空间量。流体页面实时缩放其组件以填充所有可用的浏览器宽度。

   Syntax:

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

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

例子：

这是一个基本的闪亮应用程序模板。

R

# import shiny package
library(shiny)
 
# define a page with fluid layout
ui <- fluidPage(h1("GeeksforGeeks article on shiny package in R"),
                p(style = "font-family:Impact", "My first shiny app")
)
server <- function(input, output) {}
 
shinyApp(ui = ui, server = server)

输出：

• shinyApp()：它从显式 UI/服务器对或绕过包含 Shiny 应用程序的目录路径创建 Shiny 应用程序对象。

   Syntax:

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

   shinyAppDir(appDir, options = list())

   shinyAppFile(appFile, options = list()) 

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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
  sliderInput(inputId = "num",
              label = "Choose a number",
              value = 10, min = 1, max = 1000),
  plotOutput("hist")
)
 
server <- function(input, output)
{
  output$hist <- renderPlot({
    hist(rnorm(input$num))
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui = ui, server = server)

输出：

• reactive()：它创建一个反应式表达式。反应式表达式是其结果将随时间变化的表达式。reactive() 包装一个普通表达式以创建一个反应式表达式。

   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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
  textInput(inputId = "num", label = "Choose a number",
            value = "", width = 100, placeholder = NULL),
  plotOutput("hist"),
  verbatimTextOutput("stats")
)
server <- function(input, output)
{
  # use reactive to create
  # a reactive expression
  data <- reactive({rnorm(input$num)})
   
  output$hist <- renderPlot({hist(data())})
  output$stats <- renderPrint({summary(data())})
}
 
# create shiny app object
# using shinyApp
shinyApp(ui = ui, server = server)

输出：

现在，将输入值从 50 更改为 100，看看会发生什么。

输出值（直方图和摘要）也随着输入值的变化而变化，即应用程序具有反应性。

• observeEvent()：它触发代码在服务器上运行。响应“类似事件”的响应式输入、值和表达式。

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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui = fluidPage(
  textInput(inputId = "num",
            label = "Enter a numeric value", value = "10"),
            actionButton("button", "Calculate"),
  column(8, tableOutput("table"))
)
 
server = function(input, output)
{
  # Take an action every time button is pressed
  observeEvent(input$button, {
    cat("Showing", input$num, "rows\n")
  })
   
  # Take a reactive dependency
  # on input$num, but not on any
  # of the stuff inside the function
  df <- eventReactive(input$button, {
    head(cars, input$num)
  })
  output$table <- renderTable({
    df()
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui, server)

输出：

• eventReactive()：仅响应特定值的反应式表达式。响应“类似事件”的响应式输入、值和表达式。

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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
  sliderInput(inputId = "num",
              label = "Choose a number",
              value = 25, min = 1, max = 100),
  actionButton(inputId = "go",
               label = "Update"),
  plotOutput("hist")
)
 
server <- function(input, output)
{
  data <- eventReactive(input$go, {
    rnorm(input$num)
  })
   
  output$hist <- renderPlot({
    hist(data())
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui = ui, server = server)

输出：

在这里，除非触发更新按钮，否则输出不会随输入值而变化

• actionButton()：它创建一个动作按钮或一个链接。它们的初始值为零，每次按下时递增一。

   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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
  sliderInput("obs", "Number of observations", 0, 1000, 500),
  actionButton("goButton", "Go!", class = "btn-success"),
  plotOutput("distPlot")
)
 
server <- function(input, output)
{
  output$distPlot <- renderPlot({
    input$goButton
    dist <- isolate(rnorm(input$obs))
    hist(dist)
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui, server)

输出：

一旦单击actionButton(Go!) ，输出就会更新。

• checkboxGroupInput()：它创建一组复选框，可用于独立切换多个选择。服务器将接收输入作为所选值的字符向量。

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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
  checkboxGroupInput("icons", "Choose icons:",
                     choiceNames =
                       list(icon("dog"), icon("cat"),
                            icon("fish"), icon("bug")),
                     choiceValues =
                       list("dog", "cat", "fish", "bug")),
                     textOutput("txt")
)
 
server <- function(input, output, session)
{
  output$txt <- renderText({
    icons <- paste(input$icons, collapse = ", ")
    paste("You chose", icons)
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui = ui, server = server)

输出：

• textInput()：它创建一个文本输入标签。

   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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
  textInput("txt", "Enter your text here", "Empty"),
  verbatimTextOutput("value")
)
 
server <- function(input, output)
{
  output$value <- renderText({ input$text })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui, server)

输出：

• 文本输出（）： 它创建一个文本输出元素。将反应式输出变量呈现为应用程序页面中的文本。

   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.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
 textInput(inputId = "Name", label = "Enter your name"),
 textOutput("txt")
)
 
server <- function(input, output, session)
{
  output$txt <- renderText({
    Name <- paste(input$Name, collapse = ", ")
    paste("Welcome! to geeksforgeeks ", Name)
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui = ui, server = server)

输出：

• 井面板（）： 创建一个带有略微嵌入边框和灰色背景的面板。

   Syntax: wellPanel(…)

Parameter	Description
…	UI elements to include inside the panel.

例子：

R

# import shiny package
library(shiny)
 
# define fluid page layout
ui <- fluidPage(
    sliderInput(inputId = "num",
                label = "Choose a number",
                value = 25, min = 1, max = 100),
   
 # define plot inside
 # a wellPanel
 wellPanel(plotOutput("hist"))
)
 
server <- function(input, output)
{
  output$hist <- renderPlot({
    hist(rnorm(input$num), main = input$title)
  })
}
 
# create shiny app object
# using shinyApp
shinyApp(ui = ui, server = server)

输出：

观察直方图位于灰色框（wellPanel）内。