R包shiny开发网页--8.文件上传和下载

小洁写于2018.10.7
十一假期结束地毫无感觉，在家慵懒地呆了几天。在北京总觉得一切都排的满满当当，时间总是不够用。回家后却自然切换了懒猪模式，只知道吃睡了。。。感觉亲妈对我天天加班到十二点会表示怀疑TOT

1.上传csv，选择读取参数，在网页上显示为表格

这段代码是由官网教程例9改变而来，设置read.csv函数的sep、quote参数，还可选择显示全部还是显示全部。

library(shiny)
library(shinydashboard)
header <- dashboardHeader(title = "Uploading Files")
sidebar <- dashboardSidebar(
  fileInput("file1", "Choose CSV File",
            multiple = TRUE,
            accept = c("text/csv",
                       "text/comma-separated-values,text/plain",
                       ".csv")),
  tags$hr(),
  checkboxInput("header", "Header", TRUE),
  radioButtons("sep", "Separator",
               choices = c(Comma = ",",
                           Semicolon = ";",
                           Tab = "\t"),
               selected = ","),
  radioButtons("quote", "Quote",
               choices = c(None = "",
                           "Double Quote" = '"',
                           "Single Quote" = "'"),
               selected = '"'),
  
  # Horizontal line ----
  tags$hr(),
  radioButtons("disp", "Display",
               choices = c(Head = "head",
                           All = "all"),
               selected = "head")
)
body <- dashboardBody(tableOutput("contents"))
ui <- dashboardPage(header, sidebar, body)
server <- function(input, output) {
  
  output$contents <- renderTable({
    
    req(input$file1)
    
    df <- read.csv(input$file1$datapath,
                   header = input$header,
                   sep = input$sep,
                   quote = input$quote)
    
    if(input$disp == "head") {
      return(head(df))
    }
    else {
      return(df)
    }
  })
}
shinyApp(ui,server)

上传文件的命令：fileInput
显示空行：tags$hr()
实现选择输出：if、else

2.下载

原理：把write.csv生成界面版

library(shiny)
library(shinydashboard)
header <- dashboardHeader(title = "Downloading Data")

sidebar <- dashboardSidebar(
    selectInput("dataset", "Choose a dataset:",
                choices = c("rock", "pressure", "cars")),
    downloadButton("downloadData", "Download")
)

body <- dashboardBody(tableOutput("table"))

ui <- dashboardPage(header, sidebar, body)

server <- function(input, output) {
  
  datasetInput <- reactive({
    switch(input$dataset,
           "rock" = rock,
           "pressure" = pressure,
           "cars" = cars)
  })
  
  output$table <- renderTable({
    datasetInput()
  })
  
  output$downloadData <- downloadHandler(
    filename = function() {
      paste(input$dataset, ".csv", sep = "")
    },
    content = function(file) {
      write.csv(datasetInput(), file, row.names = FALSE)
    }
  )
  
}

shinyApp(ui, server)

3.显示系统时间

library(shiny)

# Define UI for displaying current time ----
ui <- fluidPage(
  
  h2(textOutput("currentTime"))
  
)

# Define server logic to show current time, update every second ----
server <- function(input, output, session) {
  
  output$currentTime <- renderText({
    invalidateLater(1000, session)
    paste("The current time is", Sys.time())
  })
  
}

# Create Shiny app ----
shinyApp(ui, server)

invalidateLater(1000, session)代表1000毫秒后更新界面，Sys.time()代表输出系统时间。

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