如何只在Shiny中加载一次文件？

Question

I'm just wondering how to run read.csv in server.R only once? In the following code, each time that I change the input in ui.R, it takes a few seconds for the code to run read.csv, therefore I'm looking forward to load the file only once at the beginning then use the same data when input in ui.R changes. Thanks Here is my code:

ui.R

shinyUI(fluidPage(
     headerPanel("myApp"),
     fluidRow(   sidebarPanel(
    selectInput("myOptions", "myOptions:",
                list("1" = "1", 
                     "2" = "2",
                     "3" = "3"))
     )),
     hr(),
     plotlyOutput("prescription"),   
     hr()   
      ))

server.R

library(utils)
library(plotly)
library(plyr)


shinyServer(function(input, output) {


  diseases<-eventReactive({
    diseases=read.csv("diseases_94.csv",header=F)
 })


  output$prescription <- renderPlotly( {

   myDiseases=diseases
   freq=count(myDiseases,"DISEASES")

   p<-plot_ly(freq, labels = ~DISEASES, values = ~freq, type = 'pie',
        textposition = 'inside',
        textinfo = 'label+percent',
        insidetextfont = list(color = '#FFFFFF'),
        hoverinfo = 'text',
        text = ~paste(DISEASES),
        marker = list(line = list(color = '#FFFFFF', width = 1)))



 p


 })


 })

Answer 1

Use the variable outside of shinyServer . This should load the file only in the beginning.