【R shiny】一些应用记录

DT和downloadButton应用
downloadButton 中验证结果输出
添加进度条
如何确保仅在使用Shiny按下操作按钮时才触发操作
其他

DT和downloadButton应用

library(shiny)
library(DT)
ui <- shinyUI(
  fluidPage(
    titlePanel("DT test"),
    downloadButton('downloadData', 'Download'),
    
    fluidRow(
      DT::dataTableOutput("table")
    )
  )
)
server <- shinyServer(function(input, output) {
  
  output$table <- DT::renderDataTable(DT::datatable({
    mtcars
  }, rownames = FALSE))
  
  output$downloadData <- downloadHandler(
    filename = 'test.csv',
    content = function(file) {
      write.csv(mtcars, file)
    }
  )
})

shinyApp(ui,server)

downloadButton 中验证结果输出

一种情况是通过shinyjs，只有输入时，才显示下载按钮：

library(shiny)

ui <- fluidPage(
  shinyjs::useShinyjs(),
  textInput("text", "content", "", placeholder = "please insert something"),
  shinyjs::hidden(downloadButton("download"))
)

server <- function(input, output, session) {
  output$download <- downloadHandler(
    filename = "file.csv",
    content = function(file) {
      write.csv(data.frame(content = input$text), file)
    }
  )
  
  observeEvent(input$text, {
    if (input$text == "")
      shinyjs::hide("download")
    else
      shinyjs::show("download")
  })
}

shinyApp(ui, server)

另一种情况是downloadButton搭配uiOutput，即只有输出结果出现时，下载按钮才出现。

#ui端
uiOutput("download")
#server端
output$download <- renderUI({
  if(!is.null(input$file1) & !is.null(input$file2)) {
    downloadButton('OutputFile', 'Download Output File')
  }
})

https://stackoverflow.com/questions/44179974/display-download-button-in-shiny-r-only-when-output-appears-in-main-panel

添加进度条

但不是真正的程序进度。

# Only run examples in interactive R sessions
if (interactive()) {
options(device.ask.default = FALSE)
 
ui <- fluidPage(
  plotOutput("plot")
)
 
server <- function(input, output) {
  output$plot <- renderPlot({
    withProgress(message = 'Calculation in progress',
                 detail = 'This may take a while...', value = 0, {
      for (i in 1:15) {
        incProgress(1/15)
        Sys.sleep(0.25)
      }
    })
    plot(cars)
  })
}
 
shinyApp(ui, server)
}

https://shiny.rstudio.com/articles/progress.html

如何确保仅在使用Shiny按下操作按钮时才触发操作

search_tweets <- function(search) return(search)

library(shiny)
ui <- fluidPage(
  
  # Application title
  #titlePanel("Twitter Analytics"),
  
  fluidRow( 
    column( 4, titlePanel("Twitter Analytics")),
    column( 3, textOutput("mysearch") ),
    column( 4, textInput("searchstring", 
                         label = "",
                         value = "")),
    column(1, 
           br(),
           actionButton("action", "go"))
    
  )
)

server <- function(input, output) {
  
  twitter <- eventReactive(input$action,{
    search_tweets(input$searchstring)
  })
  
  output$mysearch  <- renderText({
    twitter()
  }) 
}

shinyApp(ui, server)