title: (RStudio) Shiny plotOutput with ggplot produces nothing
body: <p>I was trying to recreate Hans Rosling famous plot using Shiny output. The output turned out to be blank in the main panel where i put my plot without any warning. Can you help me point out my mistake please?</p>
  
  <pre><code>library(gapminder)  
  library(ggplot2)  
  library(shiny)  
  library(dplyr)  
  
  ui &lt;- shinyUI(fluidPage(  
     titlePanel("Life expectancy and GDP per capita from 1952 to 2007"),  
     sidebarLayout(  
    sidebarPanel(  
      p("Select year"),  
       sliderInput("yeartime",  
                   label = "Year",  
                   min = 1952,  
                   max = 2007,  
                   value = 1952,  
                   animate = animationOptions(interval = 500, loop = TRUE)
                   )),  
      mainPanel(
    plotOutput("Plot"),  
    )  
     )  
  ))
  
  continent_colours &lt;-c(Africa = "#BF590CFF", Americas = "#F80039FF", Asia = "#600071FF", 
                    Europe = "#3B9626FF", Oceania = "#4A51E0FF")  
  
  server &lt;- shinyServer(function(input, output) {  
     output$Plot &lt;- renderPlot({  
  
  p &lt;- ggplot(gapminder, aes(x=lifeExp, y=gdpPercap, size = pop, color = continent))   
    + geom_point(data = filter(gapminder,gapminder$year == input$yeartime), aes(lifeExp, gdpPercap, size = pop, color = continent_colours)) 
    + ylim(30,100) 
     + labs(x="Life expectancy (years)", y = "GDP per capita (USD)", color = 'Continent',size = "Population (millions)")
  
     })
  
  
  })
  
  
  shinyApp(ui = ui, server = server)
  </code></pre>