在R Shiny中将上传的CSV数据读取为反应值

Question

我的目标是通过Shiny将CSV上传到data.frame，然后使用CSV中的值更新其他反应式值。

library(shiny)

# Define UI for data upload app ----
ui <- fluidPage(

  # App title ----
  titlePanel("Uploading Files"),

  # Sidebar layout with input and output definitions ----
  sidebarLayout(

    # Sidebar panel for inputs ----
    sidebarPanel(

      # Input: Select a file ----
      fileInput("file1", "Choose CSV File",
                multiple = FALSE,
                accept = c("text/csv",
                           "text/comma-separated-values,text/plain",
                           ".csv")),

      # Horizontal line ----
      tags$hr(),

      # Input: Checkbox if file has header ----
      checkboxInput("header", "Header", TRUE),

      # Input: Select separator ----
      radioButtons("sep", "Separator",
                   choices = c(Comma = ",",
                               Semicolon = ";",
                               Tab = "\t"),
                   selected = ","),

      # Input: Select quotes ----
      radioButtons("quote", "Quote",
                   choices = c(None = "",
                               "Double Quote" = '"',
                               "Single Quote" = "'"),
                   selected = '"'),

      # Horizontal line ----
      tags$hr(),

      # Input: Select number of rows to display ----
      radioButtons("disp", "Display",
                   choices = c(Head = "head",
                               All = "all"),
                   selected = "head")

    ),

    # Main panel for displaying outputs ----
    mainPanel(

      # Output: Data file ----
      tableOutput("contents"),
      plotOutput("plot")
    )

  )
)

# Define server logic to read selected file ----
server <- function(input, output) {
  values <- reactiveValues(x = rnorm(100), y = rnorm(100))
  output$plot <- renderPlot({plot(values$x,values$y)})
  observeEvent(data,({
    values$x <- data()[,1]
    values$y <- data()[,2]
  }))
  data <- reactive({
  #output$contents <- renderTable({
    # input$file1 will be NULL initially. After the user selects
    # and uploads a file, head of that data file by default,
    # or all rows if selected, will be shown.

    req(input$file1)

    # when reading semicolon separated files,
    # having a comma separator causes `read.csv` to error
    tryCatch(
      {
        df <- read.csv(input$file1$datapath,
                       header = input$header,
                       sep = input$sep,
                       quote = input$quote)
      },
      error = function(e) {
        # return a safeError if a parsing error occurs
        stop(safeError(e))
      }
    )

    if(input$disp == "head") {
      return(head(df))
    }
    else {
      return(df)
    }

  })
  output$contents <- renderTable({data()})
}

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

我想要的是保留原始随机值图，直到数据上传，然后让绘制的值更改为新数据。

示例CSV可以通过以下方式从R中获取：

write.csv(faithful, "faithful.csv", row.names = FALSE)