Statistical test with file uploaded by user

Question

I am currently trying to develop an app that could realise statistical tests on any file uploaded by the user. The problem is that I often encounter problems trying to do the tests and many "error" messages appears. Here I cannot make the t-test work for example. Would you kindly care to look for the errors in my code please, as I cannot seem to find them myself. Moreover, if you by any chance have any other codes to suggest that could resemble the app I am trying to create I would gladly like to see them to get some inspiration and better understand how Shiny works. Here is the beginning of my code, Thank you so much for your attention.

library(ggplot2)
library(desctable)
ui <- fluidPage(
  tabPanel(
    "Upload File",
    titlePanel("Uploading Files"),
    sidebarLayout(
      sidebarPanel(
        fileInput('file1', 'Choose CSV File', min=0 , max=1000 , value=500
                  accept=c('.csv')),
        checkboxInput('header', 'Header', TRUE),
        radioButtons('sep', 'Separator',
                     choices = c(Comma=',', Semicolon=';', Tab='\t'),
                     selected = ','),
        
        selectInput('xcol', 'X Variable', "", selected = NULL),
        selectInput('ycol', 'Y Variable', "", selected = NULL),
        selectInput("method", "Select t test type", 
                    c("One-sample t test",
                      "Independent two-sample t test"
                    ),
                    
        ),
        mainPanel(
         
          plotOutput('MyPlot'),
          tableOutput("table"),
          verbatimTextOutput("summary")
        )
      )
    )
  )
  
  server <- function(input, output, session)
  {
    output$table<- renderDataTable(input$file1)
    
    myfiles <- reactive({
      req(input$file1$datapath, file.exists(input$file1$datapath))
      
read.csv(input$file1$datapath)
    })
output$summary<-renderPrint(myfiles%>%desctable(stars=list((“N”  =length,
       “Moyenne”= is.normal~mean,
“Médiane”=median,
“MAD”=mad))    
  observeEvent(myfiles(), {
      req(myfiles())
      nms <- colnames(myfiles())
      updateSelectInput(
        session, 
        inputId = 'xcol', 
        label = 'X Variable',
        choices = nms, selected = nms[1]
      )
      
      updateSelectInput(
        session, 
        inputId = 'ycol', 
        label = 'Y Variable',
        choices = nms, selected = nms[1]
      )
    })
    
    output$table <- renderTable({
      if(is.null(dff())){return ()}
      
      if(input$method == "One-sample t test"){
        t.test(myfiles[input$xcol], mu = as.numeric(input$mu))
        
       else if (input$method == "Independent two-sample t test"){
        t.test(input$xcol ~ input$ycol, data = myfiles)}
        
        output$MyPlot <- renderPlot({
          req(myfiles(), input$xcol, input$ycol)
          ggplot(data = myfiles(), mapping = aes_string(input$xcol, input$ycol)) +
            geom_point() +theme_dark()
           
        })}
      
      
      shinyApp(ui , server)```