避免滑块输入舍入答案

【问题标题】：Avoid sliderInput rounding避免滑块输入舍入
【发布时间】：2020-01-26 23:27:37
【问题描述】：

当最小/最大范围较大时，sliderInput 舍入我的起始值参数时遇到问题。在以下示例的情况下，如何防止 sliderInput 舍入我的起始值参数？

library(shiny)

ui <- fluidPage(
    sliderInput(
      inputId = "test",
      label = "A Nice Label",
      min = 2.52,
      max = 45734.68,
      value = 30982.63, # auto rounded to nearest integer in application, which I do not want it to do.
      round = FALSE # tried this argument, no dice.
    ),
    verbatimTextOutput(
      "value"
    )
  )

## SERVER PROCESSING DEFINITION
# this section defines how data is processed in response to manipulations in the ui
server <- function(input, output, session) {

  output$value <- renderText({
    input$test
  }) 

}

shinyApp(ui, server)

【问题讨论】：

标签： r shiny

【解决方案1】：

您需要提供step = 参数以任意提高精度。文档说默认情况下“使用启发式”来确定步长，这会导致您观察到的舍入。查看此更新版本：

library(shiny)

ui <- fluidPage(
  fluidPage(
    sliderInput(
      inputId = "test",
      label = "A Nice Label",
      min = 2.52,
      max = 45734.68,
      step = 0.01,      # the smallest level of precision in your args
      value = 30982.63, # no longer rounded
      round = FALSE     # this is the default
    ),
    verbatimTextOutput(
      "value"
    )
  )
)

## SERVER PROCESSING DEFINITION
# this section defines how data is processed in response to manipulations in the ui
server <- function(input, output, session) {

  output$value <- renderText({
    sprintf("%5.6f", input$test)       # format text to show precision
  }) 

}

shinyApp(ui, server)

如果您深入研究sliderInput，您会发现shiny:::findStepSize 的以下定义：

function (min, max, step) 
{
  if (!is.null(step)) 
    return(step)
  range <- max - min
  if (range < 2 || hasDecimals(min) || hasDecimals(max)) {
    pretty_steps <- pretty(c(min, max), n = 100)
    n_steps <- length(pretty_steps) - 1
    signif(digits = 10, (max(pretty_steps) - min(pretty_steps))/n_steps)
  }
  else {
    1
  }
}

所以你可以看到它试图在你的最小值和最大值之间有大约 100 步，所以它们会自动四舍五入为整数（甚至更大的步长）。

【讨论】：