How to get mouse over labels in a shiny ggplot2 polar plot?

Question

I'm struggeling with mouse over labels for my ggplot 2 polar plot in shiny.

Simple version of my code (without mouse over labels):

library(dplyr)
library(shiny)
library(ggplot2)

# Define UI for application that plots features of iris
ui <- fluidPage(
  br(),

  # Sidebar layout 
  sidebarLayout(

    # Inputs

    sidebarPanel( 
    ),

    # Outputs
    mainPanel(  
      plotOutput(outputId = "radarplot"), 
      br()
    )
  )
)

# Define server function required to create the radarplot
server <- function(input, output) { 

  # Create radarplot with iris dataset 
  output$radarplot  <- renderPlot ({ 
    iris %>%
      ggplot(.) + geom_histogram(aes(y = Petal.Width, x = Species, fill = Species), 
                                 binwidth= 1,
                                 stat= 'identity', 
                                 alpha = 1 ) + 
      geom_histogram(aes(y = Sepal.Width,  x = Species, fill = Species),  
                                 binwidth= 1, 
                                 stat= 'identity',
                                 alpha = 0.3) + 
      coord_polar() 


  })

}

# Create a Shiny app object
shinyApp(ui = ui, server = server)

I made a version using plotly, trying to add mouse over labels. But then I don't get a radar plot.

library(dplyr)
library(shiny)
library(ggplot2)
library(plotly)

# Define UI for application that plots features of iris
ui <- fluidPage(
  br(),

# Sidebar layout 
sidebarLayout(

# Inputs

    sidebarPanel( 
    ),

   # Outputs
      mainPanel(  
      plotlyOutput(outputId = "radarplot"), 
      br()
    )
  )
)

# Define server function required to create the radarplot
server <- function(input, output) { 

  # Create radarplot with iris dataset 
  output$radarplot  <- renderPlotly ({ 
    iris %>%
      ggplot(.) + geom_histogram(aes(y = Petal.Width, x = Species, fill = Species), 
                                 binwidth= 1,
                                 stat= 'identity', 
                                 alpha = 1 ) + 
      geom_histogram(aes(y = Sepal.Width,  x = Species, fill = Species),  
                                 binwidth= 1, 
                                 stat= 'identity',
                                 alpha = 0.3) + 
      coord_polar() 


  })

}

# Create a Shiny app object
shinyApp(ui = ui, server = server)

Ideally I want the mouse over label to give output about Petal.Width, Sepal.Width and Species when hovering over a particular Species 'wing'.

Any suggestions how to get these mouse over labels?

Answer 1

Here is an example of this using the ggiraph package. First the tooltip needs to be created.

library(tidyverse)
iris_group_means <- 
  iris %>% 
  group_by(Species) %>% 
  summarise_all(mean) %>% 
  mutate(tooltip = sprintf("Sepal Length: %1.2f\nSepal Width: %1.2f\nPetal Length: %1.2f\nPetal Width: %1.2f",
                           Sepal.Length, Sepal.Width, Petal.Length, Petal.Width)) %>% 
  select(Species, tooltip)

Then this tooltip just needs to be provided as an aesthetic, and instead of geom_histogram, use the ggiraph::geom_histogram_interactive function.

my_gg <- 
  iris %>%
  ggplot() + 
  geom_histogram(aes(y = Petal.Width, x = Species, fill = Species), 
                                      binwidth= 1, 
                                      stat= 'identity', 
                                      alpha = 1 ) + 
  ggiraph::geom_histogram_interactive(aes(y = Sepal.Width,  x = Species, fill = Species, tooltip = tooltip),
                 binwidth= 1,
                 stat= 'identity',
                 alpha = 0.3) +
  coord_polar() 
ggiraph::ggiraph(code = print(my_gg))

This can then be used in Shiny. A few other steps are involved and there is a separate ggiraph::renderggiraph function to use. Details are on the ggiraph site

Here is the final Shiny code. I don't use shiny much so this can probably be improved upon, but it worked for me.

# Define UI for application that plots features of iris
ui <- fluidPage(
  br(),

  # Sidebar layout 
  sidebarLayout(

    # Inputs

    sidebarPanel( 
    ),

    # Outputs
    mainPanel(  
      ggiraph::ggiraphOutput(outputId = "radarplot"), 
      br()
    )
  )
)

# Define server function required to create the radarplot
server <- function(input, output) { 

  # Create radarplot with iris dataset 
  output$radarplot  <- ggiraph::renderggiraph ({ 
    iris_group_means <- 
      iris %>% 
      group_by(Species) %>% 
      summarise_all(mean) %>% 
      mutate(tooltip = sprintf("Sepal Length: %1.2f\nSepal Width: %1.2f\nPetal Length: %1.2f\nPetal Width: %1.2f",
                               Sepal.Length, Sepal.Width, Petal.Length, Petal.Width)) %>% 
      select(Species, tooltip)

    iris <- 
      left_join(iris, iris_group_means, by="Species")

    my_gg <- 
      iris %>%
      ggplot() + 
      geom_histogram(aes(y = Petal.Width, x = Species, fill = Species), 
                     binwidth= 1, 
                     stat= 'identity', 
                     alpha = 1 ) + 
      ggiraph::geom_histogram_interactive(aes(y = Sepal.Width,  x = Species, fill = Species, tooltip = tooltip),
                                          binwidth= 1,
                                          stat= 'identity',
                                          alpha = 0.3) +
      coord_polar() 

    ggiraph::ggiraph(code = print(my_gg))


  })

}

# Create a Shiny app object
shinyApp(ui = ui, server = server)