Question

我正在尝试开发一个闪亮的应用程序，用户可以上传csv文件，随后由我的R脚本进行分析。因此，我希望根据处理的文件数量显示动态数量的图表（每个文件一个图表）。

我发现this问题非常有帮助，但我事先并不知道最大数量的情节。这是我试过的：

shinyServer(function(input, output) {

  # Insert the right number of plot output objects into the web page
  output$densityPlots <- renderUI({
    plot_output_list <- lapply(1:length(input$file1$datapath), function(i) {
      plotname <- paste("densityPlot", i, sep="")
      plotOutput(plotname)
    })

    # Convert the list to a tagList - this is necessary for the list of items
    # to display properly.
    do.call(tagList, plot_output_list)
  })

  # Call renderPlot for each one. Plots are only actually generated when they
  # are visible on the web page.
  for (i in 1:length(input$file1$datapath)) {
    # Need local so that each item gets its own number. Without it, the value
    # of i in the renderPlot() will be the same across all instances, because
    # of when the expression is evaluated.
    local({
      my_i <- i
      plotname <- paste("densityPlot", my_i, sep="")
      output[[plotname]] <- renderPlot({
        plot(1)
      })
    })
  }
}

然而，它给了我这个错误：

  Error in .getReactiveEnvironment()$currentContext() : 
  Operation not allowed without an active reactive context. (You tried to do something that can only be done from inside a reactive expression or observer.)

我试图将for-loop放在输出函数中，但是根本没有创建绘图。

Answer 1

我可以让它发挥作用。必须使用反应导体来创建图，如here

所述

shinyServer(function(input, output) {

  createPlots <- reactive ({ 
    numberOfFiles <- length(input$files$datapath) 
    for (i in 1:numberOfFiles) {
      local({
        my_i <- i
        plotname <- paste("plot", my_i, sep="")
        File <- read.csv(input$files$datapath[my_i]) 
        output[[plotname]] <- renderPlot({
          result <- runDensity(File, f)
          plot(result$data, main=id, pch=19,cex=0.2, col= ColoursUsed[result$clusters])
        })
      })
    }
  })

  output$densityPlot <- renderUI({

    inFile <- input$files
    if (is.null(inFile))
      return(NULL)
    createPlots()
    numberOfFiles <- length(inFile$datapath) 
    plot_output_list <- lapply(1:numberOfFiles, function(i) {
      plotname <- paste("plot", i, sep="")
      plotOutput(plotname)
    })

    do.call(tagList, plot_output_list)
  })

})

根据Shiny上传文件的数量动态创建绘图

1 个答案: