ObserveEvent 中的闪亮应用程序错误？ [.default: 无效下标类型“列表”中的错误

Question

我正在编写一个闪亮的应用程序，其中一部分包括用户输入文本以模仿 R 代码以及应用程序本身从该输入中挑选出某些单词以打印与用户调用的内容相关的向量。但是，当我尝试在应用程序中输入任何单词并按下操作按钮时，它会使程序崩溃并返回错误：Warning: E​​rror in [.default: invalid subscript type 'list'，并指示它在观察事件处理程序。事件中有一个列表，但我有一次将其取消列出，因为我无法按照我原本打算的方式使用它，而且我不确定这会如何干扰或使应用程序崩溃。我在下面提供了应用代码的相关部分：

 library(shiny)
 library(stringr)

 site <- c(rep("A", 5), rep("B", 5), rep("C", 5), rep("D", 5))
 my.num <- 1:20
 temp <- rnorm(20, 5, 1)
 growth <- 5*temp + rnorm(20, 0, 2)

  my.data <- data.frame(site = site, my.num = my.num, temp = temp, growth = growth)

 ui <- pageWithSidebar(
     headerPanel('Data Wrangler'), 
        sidebarPanel(
       p("It is important to use the right commands to be able to properly format
           your data. Let's see what it looks like when we try to use the combine function (c) tp join our variables
            instead, for instance:"),
   textInput("var.com", "Combine several of the variables using c():", NULL),
    actionButton("go6", "GO!")
   ), 
  mainPanel(
    textOutput("display2")
  ))

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

 buttonValue <- reactiveValues(go6=FALSE)

   observeEvent(input$go6, {

     isolate({
       buttonValue$go6 = TRUE
     })

     games <- names(my.data)
     tofind <- paste(games, collapse="|")

     cominput <- str_extract_all(input$var.com, tofind)

     printables <- NULL


    for (i in 1:length(cominput)){


       printables[i] <- c(my.data[cominput[i]])
       printables

     }

     working <- unlist(printables)




      output$display2 <- renderText(
      is.not.null <- function(x) !is.null(x),

      if (is.not.null(working)) {
        print(working)
      } else {
        print("Sorry, this is incorrect; check your signage.")
      }
    )





    session$onSessionEnded({
     stopApp
   }) 

 })
 }

 shinyApp(ui = ui, server = server)

所有这些都按预期工作，没有包含 Shiny 元素，因此它与 Shiny 反应性有关，不处理其中的某些元素。任何帮助将不胜感激！

编辑：下面我包含了一些预期输出的屏幕截图，使用了传递给 Shiny 之前的代码。它应该能够获取任何变量名称（“site”、“temp”、“growth”）等，并将它们粉碎在一起并将它们打印为一个长向量，以模拟如果您尝试组合会发生什么他们用 c()。该输出的演示代码如下：

   library(stringr)

   site <- c(rep("A", 5), rep("B", 5), rep("C", 5), rep("D", 5))
   my.num <- 1:20
   temp <- rnorm(20, 5, 1)
   growth <- 5*temp + rnorm(20, 0, 2)

   my.data <- data.frame(site = site, my.num = my.num, temp = temp, growth = growth)

dubbo <- c("temp", "my.num")
 games <- names(my.data)

   tofind <- paste(games, collapse="|")

    secondinput <- str_extract_all(dubbo, tofind)
    printables <- NULL


   for (i in 1:length(secondinput)){


     printables[i] <- c(my.data[secondinput[[i]]])
     printables

    }

  susus <- NULL

   susus <- unlist(printables)
    susus

预期输出：

Answer 1

您在str_extract_all 之后缺少一些错误处理，并且您试图以错误的方式访问cominput（即list()）的元素。

这是否符合您的预期？：

library(shiny)
library(stringr)

site <- c(rep("A", 5), rep("B", 5), rep("C", 5), rep("D", 5))
my.num <- 1:20
temp <- rnorm(20, 5, 1)
growth <- 5 * temp + rnorm(20, 0, 2)

my.data <-
  data.frame(
    site = site,
    my.num = my.num,
    temp = temp,
    growth = growth
  )

ui <- pageWithSidebar(
  headerPanel('Data Wrangler'),
  sidebarPanel(
    p(
      "It is important to use the right commands to be able to properly format
           your data. Let's see what it looks like when we try to use the combine function (c) tp join our variables
            instead, for instance:"
    ),
    textInput("var.com", "Combine several of the variables using c():", NULL),
    actionButton("go6", "GO!")
  ),
  mainPanel(textOutput("display2"))
)

server <- function(input, output, session) {
  buttonValue <- reactiveValues(go6 = FALSE)

  observeEvent(input$go6, {
    isolate({
      buttonValue$go6 = TRUE
    })

    games <- names(my.data)
    tofind <- paste(games, collapse = "|")

    cominput <- str_extract_all(input$var.com, tofind)

    printables <- list(NULL)

    if (identical(cominput, list(character(0)))) {
      working <- NULL
    } else {
      for (i in 1:length(unlist(cominput))) {
        printables[i] <- c(my.data[cominput[[1]][i]])
      }
      working <- unlist(printables)
    }

    output$display2 <- renderText(if (!is.null(working)) {
      print(working)
    } else {
      print("Sorry, this is incorrect; check your signage.")
    })

    session$onSessionEnded({
      stopApp
    })

  })
}

shinyApp(ui = ui, server = server)