Using read.xlsx in Shiny R App

问题

I am trying to load an excel file and display the summary. The file is loading without any errors but not displaying anything.

Here is my code

ui.R

library(shiny)
shinyUI(pageWithSidebar(
     headerPanel("Analysis"),
     sidebarPanel(wellPanel(fileInput('file1', 'Choose XLSX File',
          accept=c('sheetName', 'header'), multiple=FALSE))),
mainPanel(
tabsetPanel(
  tabPanel("Tab1",h4("Summary"), htmlOutput("summary"))    
)))

server.R

      library(shiny)


shinyServer(function(input, output) {
 dataset = reactive({

    infile = input$file1  


    if (is.null(infile))
      return(NULL)

    infile_read = read.xlsx(infile$datapath, 1)
    return(infile_read)

  })

 output$summary <- renderPrint({
   summary = summary(dataset())
   return(summary)
 })

  outputOptions(output, "summary", suspendWhenHidden = FALSE)

})

回答1:

I haven't tested this, but it looks like you're not actually returning anything from dataset(). Change the function to:

dataset = reactive({

  infile = input$file1  

  if (is.null(infile))
    return(NULL)

  read.xlsx(infile$datapath, 1)

})

When you do infile_read = read.xlsx(infile$datapath, 1), you're reading the file into infile_read but then you're not actually returning it. Reactives work just look any R function really. Try running this:

f <- function() x <- 10
f()

You should see that f() doesn't return anything. All it's doing is making an assignment that goes nowhere. To actually return 'hello' you would do:

f <- function() {
  x <- 'hello'
  x
}

Or just:

f <- function() 'hello'

来源：https://stackoverflow.com/questions/18727284/using-read-xlsx-in-shiny-r-app