R闪亮的renderImage()不识别对象‘输入’

Question

为什么renderImage()在下面的代码示例中不识别input：

library(d3heatmap)
library(shiny)
library(ggplot2)


    ui <- fluidPage(
      h1("A heatmap demo"),
      selectInput("palette", "Palette", c("YlOrRd", "RdYlBu", "Greens", "Blues")),
      checkboxInput("cluster", "Apply clustering"),
      downloadButton('downloadPlot', 'Download Heatmap'),
      d3heatmapOutput("heatmap")
)

    server <- function(input, output, session) {

      output$heatmap <- renderD3heatmap({
        d3heatmap(
          scale(mtcars),
          colors = input$palette,
          dendrogram = if (input$cluster) "both" else "none"
) })

    output$downloadPlot <- renderImage(
        d3heatmap(scale(mtcars), colors = input$palette, dendrogram = if (input$cluster) "both" else "none"), 
        env = parent.frame(), 
        quoted = FALSE, 
        deleteFile = FALSE
        )

    }

shinyApp(ui = ui, server = server)

这是我的错误：

Error in match.arg(dendrogram) : object 'input' not found

删除dendrogram = if (input$cluster) "both" else "none"行时，再次得到有关input的以下错误：

Error in toPaletteFunc(pal) : object 'input' not found

没有找到input对象似乎有点违背直觉，因为我已经在楼上使用：server <- function(input, output, session)明确地定义了它。

我已经检查了生成类似错误消息(例如，发亮的错误:找不到对象输入)的现有堆栈溢出帖子。

以上代码示例的灵感来自：https://cran.r-project.org/web/packages/d3heatmap/d3heatmap.pdf

Answer 1

d3heatmap()生成htmlwidgets类对象。我们可以使用来自saveWidget()包的htmlwidgets函数来保存绘图。

library(d3heatmap)
library(shiny)
library(htmlwidgets)

ui <- fluidPage(
    h1("A heatmap demo"),
    selectInput("palette", "Palette", c("YlOrRd", "RdYlBu", "Greens", "Blues")),
    checkboxInput("cluster", "Apply clustering"),
    downloadButton('download', 'Download Heatmap'),
    d3heatmapOutput("heatmap")
)
server <- function(input, output, session) {
    plot <- reactive({
        d3heatmap(
            scale(mtcars),
            colors = input$palette,
            dendrogram = if (input$cluster) "both" else "none"
        )
    })
    output$heatmap <- renderD3heatmap({
        plot()
    })
    output$download <- downloadHandler(
        filename = function() {
            paste0("d3heatmap-", tolower(input$palette), ".html")
        },
        content = function(file) {
            saveWidget(plot(), file)
        }
    )
}

shinyApp(ui = ui, server = server)

如果需要将绘图保存为png，请参见下面的讨论：https://github.com/ramnathv/htmlwidgets/issues/95。简而言之:现在htmlwidgets不支持像png或svg这样的导出地块。您可以看到出口品和网照包是工作区。