为什么这个 Shiny App 不使用 RStudio 显示数据框？

Question

I have a list of data frames, ls_df , comprising two dataframes from the datasets package.

I am trying to load these two dataframes into a Shiny app using the code below. However, it does not work, with the error message no item called "ls_df" on the search list being returned. Does anyone know how to fix?

ls_df <- list(datasets::airmiles,
datasets::AirPassengers)


ui <- fluidPage(
  selectInput("ls_df", label = "Dataset", choices = ls("ls_df")),
  verbatimTextOutput("summary"),
  tableOutput("table")
)

server <- function(input, output, session) {
  output$summary <- renderPrint({
    dataset <- get(input$ls_df, "ls_df")
    summary(dataset)
  })
  
  output$table <- renderTable({
    dataset <- get(input$ls_df, "ls_df")
    dataset
  })
}
shinyApp(ui, server)

Answer 1

The list needs the names:

library(shiny)
ls_df <- list(airmiles=datasets::airmiles,AirPassengers=datasets::AirPassengers)

ui <- fluidPage(
  selectInput("ls_df", label = "Dataset", choices = names(ls_df)),
  verbatimTextOutput("summary"),
  tableOutput("table")
)

server <- function(input, output, session) {
  output$summary <- renderPrint({
    dataset <- ls_df[[input$ls_df]]
    summary(dataset)
  })
  
  output$table <- renderTable({
    dataset <- ls_df[[input$ls_df]]
    dataset
  })
}
shinyApp(ui, server)

Answer 2

Two things wrong:

1. Your list needs names, as discussed in PorkChop's answer. If this were the only required change, then PorkChop's answer would suffice.

2. get(input$ls_df, "ls_df") is an error. This should be rather clear, though, since it prevents the shiny interface from starting. This error is because the envir= argument of ls and get require an object , not the character name of an object. (One could go "inception" and use ls(get("ls_df")) and similarly for get , but that hardly seems necessary or useful.)

    ls_df <- list(airmiles=datasets::airmiles, # <-- named list AirPassengers=datasets::AirPassengers) ui <- fluidPage( selectInput("ls_df", label = "Dataset", choices = ls(ls_df)), # <-- no quotes verbatimTextOutput("summary"), tableOutput("table") ) server <- function(input, output, session) { output$summary <- renderPrint({ dataset <- get(input$ls_df, ls_df) # <-- no quotes summary(dataset) }) output$table <- renderTable({ dataset <- get(input$ls_df, ls_df) # <-- no quotes dataset }) }