title: tooltip on shiny R?
body: <p>I want to have a tool-tip in my <code>Shiny</code> <code>R</code> application. Is there any easy way to achieve that? For now, I am creating a density map and I want a simple tool-tip showing "click here to slide through years" while hovering the mouse over slider YEAR. <br/></p>
  
  <p>User Interface:<br/></p>
  
  <pre><code>library(shiny)
  shinyUI(pageWithSidebar(
    headerPanel("Density Map"),
    sidebarPanel(
      sliderInput("slider_year", "YEAR:", 
                  min = 2001, max = 2011, value = 2009, 
                  format="####", locale="us"
      )
    )
   ),
  
    mainPanel(  
      plotOutput("event_heatmap_map", width = "100%", height = "100%")
    )
  ))
  </code></pre>
  
  <p><br/>
  Server Code:</p>
  
  <pre><code>library(shiny)
  library(ggmap)
  library(ggplot2)
  mydata &lt;- read.csv("/var/shiny-server/www/dMetrics.csv")
  shinyServer(function(input, output) {
      output$event_heatmap_map &lt;- renderPlot(width = "auto", height = 640,{
  
          slice_year &lt;- mydata[mydata$YEAR==input$slider_year,]
          map &lt;- get_map(c(lon = -55.3632715, lat = 31.7632836), zoom = 3, source = 'google', maptype = c("terrain"), messaging = FALSE, color = 'color')
          world &lt;- ggmap(map)
          world &lt;- world + stat_density2d(data = slice_year, aes(x = WEST, y = NORTH, fill = ..level.., alpha = ..level..), show_guide = FALSE, geom = "polygon", na.rm = TRUE) + scale_fill_gradient(name="Density", low="maroon", high="yellow", guide = 'colorbar')
          plot(world)
      })
  })
  </code></pre>
  
  <p>Thanks for the help.</p>