带有rCharts的R闪亮应用

我可以使用rCharts创建此图：

library(rCharts)
X <- structure(list(Var1 = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 
                                       8L, 9L, 10L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 1L, 2L, 
                                       3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L), .Label = c("1", "2", "3", "4", 
                                                                                    "5", "6", "7", "8", "9", "10"), class = "factor"), Var2 = structure(c(1L, 
                                                                                                                                                          1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
                                                                                                                                                          2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("control", 
                                                                                                                                                                                                                          "treatment1", "treatment2"), class = "factor"), Freq = c(0L, 
                                                                                                                                                                                                                                                                                   0L, 3L, 2L, 6L, 9L, 13L, 36L, 50L, 497L, 0L, 2L, 1L, 3L, 6L, 
                                                                                                                                                                                                                                                                                   4L, 11L, 29L, 50L, 499L, 1L, 2L, 0L, 2L, 5L, 6L, 12L, 22L, 63L, 
                                                                                                                                                                                                                                                                                   490L)), .Names = c("Var1", "Var2", "Freq"), row.names = c(NA, 
                                                                                                                                                                                                                                                                                                                                             -30L), class = "data.frame")
n1<-nPlot(Freq ~ Var1, group = 'Var2', data = X, type = 'multiBarChart')
print(n1)

现在，我正在尝试嵌入Shiny应用程序。我可以使用ggplot2做一个闪亮的应用程序，但是我不确定如何打印rCharts图。

这是我现在拥有的闪亮代码：

#server.R
library(rCharts)
X <- structure(list(Var1 = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 
                                       8L, 9L, 10L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 1L, 2L, 
                                       3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L), .Label = c("1", "2", "3", "4", 
                                                                                    "5", "6", "7", "8", "9", "10"), class = "factor"), Var2 = structure(c(1L, 
                                                                                                                                                          1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
                                                                                                                                                          2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("control", 
                                                                                                                                                                                                                          "treatment1", "treatment2"), class = "factor"), Freq = c(0L, 
                                                                                                                                                                                                                                                                                   0L, 3L, 2L, 6L, 9L, 13L, 36L, 50L, 497L, 0L, 2L, 1L, 3L, 6L, 
                                                                                                                                                                                                                                                                                   4L, 11L, 29L, 50L, 499L, 1L, 2L, 0L, 2L, 5L, 6L, 12L, 22L, 63L, 
                                                                                                                                                                                                                                                                                   490L)), .Names = c("Var1", "Var2", "Freq"), row.names = c(NA, 
                                                                                                                                                                                                                                                                                                                                             -30L), class = "data.frame")

shinyServer(
  function(input, output) {
    output$histogram <- renderPlot({
      # You can access the value of the widget with input$select, e.g.
      output$value <- renderPrint({ input$select })
      n2 <- nPlot(Freq ~ Var1, group = 'Var2', data = X, type = 'multiBarChart')
      n2$set(dom = "histogram")
      return(n2)
      })
  }
)

#ui.R
shinyUI(fluidPage(
  titlePanel("Quiz 3 grades distribution"),

  sidebarLayout(
    sidebarPanel(
      helpText("Quiz 3 grade distribution by treatment group"),    
      selectInput("select", label = h3("Select box"), 
                  choices = list("All" = 0, "Not Perfect" = 1, "Perfect" = 2), 
                  selected = 0)
    ),

    mainPanel(plotOutput("histogram"))
  )
))

我究竟做错了什么？谢谢！