无法使我的R闪亮应用显示ggplot图形

Question

我正在尝试在我的R Shiny应用程序上显示反应式ggplot，但是它不起作用，我不确定为什么。如果有人可以指出为什么它不起作用，将不胜感激。

下面是我的代码：

1。 ui

ui <- fluidPage(titlePanel("Sample Size Calculator for Binary     Covariates from Dog Data Based on Heish et. al (1998)"),
            helpText("This sample size Calculator is based on the paper 'A Simple Method of Sample Size Calculation for Linear and Logistic Regression' by Heish et al. (1998)",
                     "This calculator treats each covariate as a binary variable, based on the cutoff point of your choice.",
                     "The set of covariates considered in the model are those set of covariates in which their desirable cutoff levels were successfully identified by their ROC curves. ",
                     "Please select Significance Level, and  Cutoff Levels of each covariate that you would like to implement. The plot of Sample Size vs. Power will be displayed below:"),   
  selectInput("diagType", "Diagnosis Outcome of Interest:", c("Cancer", "Sepsis", "SIRS")),
  selectInput("alpha1", "Significance Level:", c("0.05", "0.01", "0.001")),
 conditionalPanel( condition = "input.diagType == 'Cancer'",
                sliderInput("bin1", label = "Cut off level for TK:", min=1, max=20, value=10),
                sliderInput("bin2", label = "Cut off level for AGE:", min=3, max=12, value=6),
                sliderInput("bin3", label = "Cut off level for BW:", min=1, max=40, value=20)),
  conditionalPanel( condition = "input.diagType == 'Sepsis'",
                sliderInput("bin4", label = "Cut off level for CRP:", min=1, max=45, value=22.5),
                sliderInput("bin5", label = "Cut off level for WBC:", min=13, max=25, value=12.5),
                sliderInput("bin6", label = "Cut off level for Temp:", min=103, max=106, value=103)),
  conditionalPanel( condition = "input.diagType == 'SIRS'",
                sliderInput("bin7", label = "Cut off level for CNP:", min=7, max=16, value=8),
                sliderInput("bin8", label = "Cut off level for Pulse:", min=104, max=180, value=135)),

  mainPanel(plotOutput("plot"))
  )

2。服务器

 server <- function(input, output) {
 d  <- reactive({

   power.vec = c(0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95)

if(input$diagType == "Cancer"){
a = input$alpha1  
b1 = input$bin1
b2 = input$bin2
b3 = input$bin3
e<-calculator.cancer(a,b1,b2,b3)
}

if(input$diagType == "Sepsis"){
  a = input$alpha1  
  b4 = input$bin4
  b5 = input$bin5
  b6 = input$bin6
  e<-calculator.sepsis(a,b4,b5,b6)
} 

  if(input$diagType == "SIRS"){
   a = input$alpha1  
   b7 = input$bin7
   b8 = input$bin8
   e <-calculator.sirs(a,b7,b8)
   }
 })

 output$plot <- renderPlot({
       b <- d()
       p <- ggplot(b, aes(x = power.vec, y = e) + labs(
                                            x = "Level of Power",
                                            y = "Sample Size",
                                            title = "Plot of Sample Size versus Power") + geom_point() + geom_line())
   print(p)

      })
  }
shinyApp(ui, server) 

为什么我的ggplot无法显示？谢谢