如何在 R Shiny 应用程序中使用工作区对象

Question

我希望用户能够输入数据框对象的名称，并将该对象呈现为 Shiny 应用程序中的格式化数据表。

这是一个玩具示例。工作区中有两个可用的数据框对象：df1 和 df2。当用户输入df1 时，我希望呈现该数据框。对于df2 或他们在工作区中拥有的任何其他数据框也是如此。

我怀疑我必须对环境、范围界定或评估做一些事情，但我不确定是什么。

我在代码中注释了我可以在内置mtcars 数据集中进行硬编码并正确呈现的代码。现在我只想能够对用户工作区中的任何临时数据框执行相同的操作。

library(shiny)
set.seed(1234)

x <- sample.int(n = 20)
y <- sample(x = LETTERS, size = 20)
a <- rnorm(n = 20)
b <- sample(x = letters, size = 20)

df1 <- data.frame(x = x, y = y)
df2 <- data.frame(a = a, b = b)


# Define UI ----
ui <- fluidPage(
  titlePanel("Using text inputs to select dataframes"),

  sidebarLayout(position = "left",
                sidebarPanel(width = 5,
                            textInput("dfInput", h5("Enter name of dataframe"),
                                                value = "")),

                mainPanel(width = 6,
                          h4("Here's your data"),
                          textOutput("selected_df"),
                          dataTableOutput("view")
                )

  )
)


# Define server logic ----
server <- function(input, output, session) {

  output$selected_df <- renderText({
    paste("You have selected ", input$dfInput)
  })

  output$view <-
    renderDataTable({
      input$dfInput # this should render the selected dataframe. If you replace this with mtcars then that dataset is correctly rendered.
    })

}


# Run the app ----
shinyApp(ui = ui, server = server)

Answer 1

我们将首先获取全局环境中的所有数据帧，然后使用get 来访问对象。我将textInput 更改为selectInput，因此您无需输入任何内容，可能会出错。此外，我添加了来自 datasets 包的数据，但是您应该构建更多测试用例来检查数据是否存在

library(shiny)
set.seed(1234)

x <- sample.int(n = 20)
y <- sample(x = LETTERS, size = 20)
a <- rnorm(n = 20)
b <- sample(x = letters, size = 20)

df1 <- data.frame(x = x, y = y)
df2 <- data.frame(a = a, b = b)

mydataframes <- names(which(unlist(eapply(.GlobalEnv,is.data.frame))))
OpenData <- data()$results[,3]

#Define UI ----
ui <- fluidPage(
  titlePanel("Using text inputs to select dataframes"),

  sidebarLayout(position = "left",
                sidebarPanel(width = 5,
                             selectInput("dfInput","Select Dataframe",
                               #choices = mydataframes,

                               list("Your Datasets" = c(mydataframes),
                                    "R Datasets" = c(OpenData),


                               selected=NULL))),

                mainPanel(width = 6,
                          h4("Here's your data"),
                          textOutput("selected_df"),
                          dataTableOutput("view")
                )

  )
)


# Define server logic ----
server <- function(input, output, session) {

  output$selected_df <- renderText({
    paste("You have selected ", input$dfInput)
  })

  output$view <-
    renderDataTable({
      as.data.frame(get(input$dfInput)) # this should render the selected dataframe. If you replace this with mtcars then that dataset is correctly rendered.
    })

}


# Run the app ----
shinyApp(ui = ui, server = server)