R shiny写一个简单的功能

初学shiny，实现一个简单的功能：上传VCF文件，输出不同SNP数量图

shiny代码：

library(shiny)
library(vcfR)
library(tidyr)
library(ggplot2)
source("VCF.R")
# Define UI ----
ui <- fluidPage(
  #titlePanel("title panel"),
  
  
  fluidRow(
    column(4,fileInput("counts", multiple = FALSE, accept = c(".vcf",".gz"), h3("Input your vcf file.")))
  ),
  
    fixedRow(
      
      column(4,actionButton("run", label = "Plot", icon = icon("paper-plane")))
      
    ),
  
    hr(),
  
    fixedRow(
      
      
    column(1,downloadButton("downloadData", "Save PDF")),
  
    column(1,downloadButton("downloadData1", "Save PNG")),
  ),
  
  
  
  fixedRow(  
    mainPanel(plotOutput("map"))
  )
)

# Define server logic ----
server <- function(input, output) {
  
  td <- getwd()
  
  options(shiny.maxRequestSize=100*1024^2)
  
  data