错误：缺少参数，没有默认值

Question

library(shiny)

dataset <- new_historydata

shinyUI(fluidPage(
  title = 'MEEDA v2.0',
  sidebarLayout(
    sidebarPanel(
      tabsetPanel(type= "tabs",

          tabPanel(("Historydata"), 
        fluidRow(
          column(4,
        selectInput("Costs", "Select Type :", c("All", 
                   list( "total_cost"= 1, "lease_cost" = 2)),selected = "All", multiple= T),
        selectInput("Variables", "Select Variables :", c( "All",
                    names(new_historydata)), selected = "All", multiple= T),
    # List of devices in the data
        selectInput("equipcategory", "Select Device :", c("All",
                  levels(historydata$equipmentcategoryx)),selected = "All", multiple= T))
          ),

        fluidRow(
          dataTableOutput("table1"))
    ),

    tabPanel(("Plot"), 

    plotOutput('plot1'),
  fluidRow(    
      title = "Variable Comparison",

    hr(),
      column(3,
             h4("Variable Comparison"),
             sliderInput('sampleSize', 'Sample Size', 
                         min=1, max=nrow(dataset),
                         value= min(1000, nrow(dataset)),
                         step=500, round=0),
             br(),
             ),
      column(4, offset = 1,
             selectInput('x', 'X', names(dataset)),
             selectInput('y', 'Y', names(dataset), names(dataset[[1]]))
      )
    )),

    tabPanel(("Calculations"),
      helpText("Module Under Construction"),
  fluidRow(
    dataTableOutput("table2"),
    ))
    )
    )
   )
  ))