r - Shiny 的 slider 输入从最大值到最小值

Question

是否可以制作一个以降序显示值的 slider 输入(从左到右；例如 5 4 3 2 1)？

runApp(
 list(
  ui = fluidPage(
   sliderInput("test","", min=5, max=1, value = 3, step=1)
   ),
   server = function(input,output) {}
  )
 )

Answer 1

编辑 2017-10-13:此功能现已在包 shinyWidgets 中提供(使用不同的名称:sliderTextInput())。

嗨，您可以像这样编写自己的 slider 函数(这有点脏......):

sliderValues <- function (inputId, label, values, from, to = NULL, width = NULL) {
        sliderProps <- shiny:::dropNulls(list(class = "js-range-slider", 
                                      id = inputId,  
                                      `data-type` = if (!is.null(to)) "double",
                                      `data-from` = which(values == from) - 1,
                                      `data-to` = if (!is.null(to)) which(values == to) - 1,
                                      `data-grid` = TRUE,
                                      `data-values` = paste(values, collapse = ", ")
                                      ))
        sliderProps <- lapply(sliderProps, function(x) {
          if (identical(x, TRUE)) 
            "true"
          else if (identical(x, FALSE)) 
            "false"
          else x
        })
        sliderTag <- div(class = "form-group shiny-input-container", 
                         style = if (!is.null(width)) 
                           paste0("width: ", validateCssUnit(width), ";"), 
                         if (!is.null(label)) 
                           shiny:::controlLabel(inputId, label), do.call(tags$input, 
                                                                 sliderProps))
        dep <- list(htmltools::htmlDependency("ionrangeslider", "2.0.12", c(href = "shared/ionrangeslider"), 
                                   script = "js/ion.rangeSlider.min.js",
                                   stylesheet = c("css/ion.rangeSlider.css",
                                                  "css/ion.rangeSlider.skinShiny.css")))
        htmltools::attachDependencies(sliderTag, dep)
      }

这样做的重点是使用 values来自 ionrangeslider 的属性(请参阅使用自定义值数组 here 部分)

缺点是您在服务器端检索的输入值不是 slider 的值，而是值的索引(从 0 开始)。

您可以像这样使用此功能:

library("shiny")
runApp(
  list(
    ui = fluidPage(
      # you have to pass the values you want in the slider directly to th function
      sliderValues(inputId = "test", label = "", from = 5, values = 5:1),
      verbatimTextOutput(outputId = "slidervalue")
    ),
    server = function(input,output) {
      output$slidervalue <- renderPrint({
        # Careful ! : input$test isn't the expected value !!!
        (5:1)[input$test + 1]
      })
    }
  )
)

还有好处:它也适用于字符向量:

runApp(
  list(
    ui = fluidPage(
      sliderValues(inputId = "test", label = "", from = "g", to = "o", values = letters),
      verbatimTextOutput(outputId = "slidervalue")
    ),
    server = function(input,output) {
      output$slidervalue <- renderPrint({
        # Careful ! : input$test isn't the expected value !!!
        letters[input$test + 1]
      })
    }
  )
)