ToolTip when you mouseover a ggplot on shiny

Question

I am building a shiny application.

I am plotting charts using ggplot.

When I mouseover the points on the graph, I want a tooltip showing one of the columns i

Answer 1

You can also use a little bit JQuery and conditional renderUI to show a custom tooltip near the pointer.

library(shiny)
library(ggplot2)

ui <- fluidPage(

  tags$head(tags$style('
     #my_tooltip {
      position: absolute;
      width: 300px;
      z-index: 100;
     }
  ')),
  tags$script('
    $(document).ready(function(){
      // id of the plot
      $("#plot1").mousemove(function(e){ 

        // ID of uiOutput
        $("#my_tooltip").show();         
        $("#my_tooltip").css({             
          top: (e.pageY + 5) + "px",             
          left: (e.pageX + 5) + "px"         
        });     
      });     
    });
  '),

  selectInput("var_y", "Y-Axis", choices = names(mtcars), selected = "disp"),
  plotOutput("plot1", hover = hoverOpts(id = "plot_hover", delay = 0)),
  uiOutput("my_tooltip")
)

server <- function(input, output) {

  data <- reactive({
    mtcars
  })

  output$plot1 <- renderPlot({
    req(input$var_y)
    ggplot(data(), aes_string("mpg", input$var_y)) + 
      geom_point(aes(color = factor(cyl)))
  })

  output$my_tooltip <- renderUI({
    hover <- input$plot_hover 
    y <- nearPoints(data(), input$plot_hover)[ ,c("mpg", input$var_y)]
    req(nrow(y) != 0)
    verbatimTextOutput("vals")
  })

  output$vals <- renderPrint({
    hover <- input$plot_hover 
    y <- nearPoints(data(), input$plot_hover)[ , c("mpg", input$var_y)]
    # y <- nearPoints(data(), input$plot_hover)["wt"]
    req(nrow(y) != 0)
    # y is a data frame and you can freely edit content of the tooltip 
    # with "paste" function 
    y
  })
}
shinyApp(ui = ui, server = server)

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EDITED:

After this post I searched internet to see whether it could be done more nicely and found this wonderful custom tooltip for ggplot. I believe it can hardly be done better than that.