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Interactive pie-chart glyphs

Source: vignettes/interactive-pie-glyphs.Rmd
interactive-pie-glyphs.Rmd

Static pie-chart glyphs can only show information about the relative proportions of the different categories. Sometimes, information about the raw counts of categories could also be important. The geom_pie_interactive function can be used in conjunction with the ggiraph framework to create interactive visualisations where hovering over a pie-glyph shows additional information about the categories shown.

All the interactive parameters from ggiraph are supported and the plots can be fully customised. A few useful examples are shown here. See ggiraph book for all available options.

Load libraries
Simulate raw data 
set.seed(737)
plot_data <- data.frame(response = rnorm(15, 100, 30),
                        system = 1:15,
                        group = sample(size = 15, x = c('G1', 'G2', 'G3'), replace = T),
                        A = round(runif(15, 3, 9), 2),
                        B = round(runif(15, 1, 5), 2),
                        C = round(runif(15, 3, 7), 2),
                        D = round(runif(15, 1, 9), 2))

The data has 15 observations and seven columns. response is a continuous variable measuring system output while system describes the 15 individual systems of interest. Each system is placed in one of three groups shown in group. Columns A, B, C, and D measure system attributes.

head(plot_data)
#>    response system group    A    B    C    D
#> 1 102.76403      1    G3 3.61 3.88 5.27 1.99
#> 2  88.77571      2    G2 7.71 2.28 3.95 6.78
#> 3  92.25642      3    G3 8.88 3.88 3.38 4.33
#> 4 147.14691      4    G3 7.14 1.57 6.45 4.27
#> 5 140.65072      5    G3 6.35 1.63 3.41 5.53
#> 6  91.95466      6    G3 7.74 2.26 5.41 1.91

Create basic interactive visualisation

Creating interactive pie-chart glyphs is similar to creating their static counterparts, we just use geom_pie_interactive instead of geom_pie_glyph and wrap the ggplot object in the girafe() function.

# Same ggplot call as the static version
gg_obj <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # geom_pie_interactive instead of geom_pie_glyph
  geom_pie_interactive(slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  theme_classic(base_size = 16)
  
# Pass the ggplot object to the girafe function to create the interactive plot
girafe(ggobj = gg_obj)

By default, hovering over a specific pie-glyph would present a tooltip containing information about the raw values and percentages of the different categories shown in that pie-glyph.

Custom tooltip

The tooltip aesthetic can be modified to show a custom tooltip when hovering over a pie-glyph. This could either be set to a column in the data, a particular character string or a combination of two.

We create a plot with the tooltip showing the group variable in the data.

gg_obj <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # specify tooltip aesthetic
  # wrapped in paste0 to add more descriptive text to the tooltip
  geom_pie_interactive(aes(tooltip = paste0("Group: ", group)),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  theme_classic(base_size = 16)
  
# Pass the ggplot object to the girafe function to create the interactive plot
girafe(ggobj = gg_obj)

Hovering over a pie-glyph will now show the group that observation belongs to.

Showing information on clicking pie-glyphs

The onclick aesthetic can be configured to execute javascript code when a pie-glyph is clicked. This could be useful in a shiny application for populating a container with information or for running javascript code like opening a webpage or making an API call based on the observations selected by the user in a plot. We show a basic example that opens up an alert box showing the group variable of the observation clicked by the user.

gg_obj <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # specify onclick aesthetic
  geom_pie_interactive(aes(
                       onclick = "alert(\"This observation belongs to group \" + 
                                  this.getAttribute(\"data-id\"))"),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  theme_classic(base_size = 16)

# Pass the ggplot object to the girafe function to create the interactive plot
girafe(ggobj = gg_obj)

Click on any pie-glyph to show a dialog box containing information about the group of the observation.

Group pie-glyphs using data_id

If the data has a grouping variable, the visualisation can be configured to highlight all the pie-glyphs for observations belonging to the same group as that of the hovered pie-glyph. This is accomplished using the data_id aesthetic.

gg_obj <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # specify data_id aesthetic
  geom_pie_interactive(aes(data_id = group),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  theme_classic(base_size = 16)
  
# Pass the ggplot object to the girafe function to create the interactive plot
girafe(ggobj = gg_obj)

Hovering over a pie-glyph would now highlight it in addition to showing the tooltip.

Customising the aesthetics of interactivity

The options argument in the girafe() function can be used to customise the aesthetic properties of the tooltip (using opts_tooltip()), hover animation(using opts_hover() and opts_hover_inv()) and general visual aesthetics (using opts_sizing(), opts_toolbar(), opts_zoom(), etc.) of the plot using CSS. We show an example modifying a few of these properties, refer to Customising girafe animations in the ggiraph book for more information.

# Reuse the previous gg_obj
girafe(ggobj = gg_obj,
       options = list(
         # Options for formatting the appearance of the tooltip
         # The tooltip will have a blue background with white text
         opts_tooltip = opts_tooltip(css = "background-color:blue;color:white;padding:5px"),
         # Options for changing animation of observations which are hovered
         # Hovered pie-glyph will be highlighted yellow with dark grey border
         opts_hover(css = "fill:yellow;stroke:darkgrey;"),
         # Options for changing properties of the pie-glyphs not selected
         # Make non-selected pie-glyphs fade into background
         opts_hover_inv(css = "opacity:0.25;"),
         # Options for panning and zooming
         # Set max to a number greater than 1 and tooltip will appear on 
         # top right giving options for panning and zooming across the plot
         opts_zoom(max = 3)
       ))

Hover over a pie-glyph to show the customised tooltip. The highlighted pie-glyph would have a different appearance while those not selected would fade into the background. The menu on the top right can also be used to pan and zoom across the plot.

Selection of observations in a plot

The opts_selection() function can be used to configure properties for selecting observations by dragging the mouse across the plot. The type = "single" allows for selecting a single value while type="multiple" enables lasso selection for selecting multiple values. A toolbar appear on top-right with options for selecting and deselecting observations.

Note: It is important to specify the data_id aesthetic (ideally a unique identifier for each observation) for performing selection.

# Add a unique identifier for each observertion
plot_data$id <- 1:nrow(plot_data)

gg_obj <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # specify data_id as a unique identifier for each observation
  geom_pie_interactive(aes(data_id = id),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  theme_classic(base_size = 16)

girafe(ggobj = gg_obj,
       options = list(
         # Options for selecting observations
         # only_shiny = FALSE is needed to see selections in page
         opts_selection(type = "multiple", 
                        only_shiny = FALSE),
         # Panning and zooming
         opts_zoom(max = 3)
       ))

Use the menu from the top right menu to perform lasso selection/deslection to select/deselect observations in the plot and zoom and pan across the plot.

Selection across multiple plots

It is also possible to arrange multiple plots beside each other and perform selection between plots. The two plots can be arranged using cowplot or patchwork and if they share the same data_id attribute, hovering over an observation in one plot would highlight that observation in the other plot.

# Lets first add two more variables to our data
set.seed(373)
plot_data <- plot_data %>% 
  mutate(response2 = round(rnorm(15, 100, 30), 2),
         system2 = round(runif(15, 5, 20), 2))

gg_obj1 <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # specify data_id as a unique identifier for each observation
  geom_pie_interactive(aes(data_id = id),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  theme_classic(base_size = 16) +
  theme(legend.position = "top")


gg_obj2 <- ggplot(data = plot_data, aes(x = system2, y = response2)) + 
  # specify data_id as a unique identifier for each observation
  geom_pie_interactive(aes(data_id = id),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  scale_fill_brewer(palette = "Dark2") + 
  labs(x = "Another system", y = "Another response") +
  theme_classic(base_size = 16) +
  theme(legend.position = "top")

girafe(ggobj = cowplot::plot_grid(gg_obj1, gg_obj2, 
                                  nrow = 1),
       options = list(
         # Options for selecting observations
         # only_shiny = FALSE is needed to see selections in page
         opts_selection(type = "multiple", 
                        only_shiny = FALSE)
       ))

Hover over a pie-glyph in any plot to see the corresponding pie-glyph in the other plot. Use the lasso selection option from the top-right menu to select multiple observations between the plots.

Combining with other interactive geoms/elements from ggiraph

geom_pie_interactive can be combined with other elements of ggiraph like geoms, scales, facets, etc. to convert every component of a plot interactive. In this example, every element of the plot including the pie-glyphs, facet labels, plot title, axis title and text, legend title and keys are interactive and they can be hovered over or clicked on to present additional information or execute javascript code in the background.

gg_obj <- ggplot(data = plot_data, aes(x = system, y = response)) + 
  # Simple theme for plot
  theme_classic(base_size = 16) +
  # Title for plot
  labs(title = "This is a plot with each component being interactive") +
  # Interactive pie-glyphs
  geom_pie_interactive(aes(data_id = id),
                       slices = c("A", "B", "C", "D"),
                       colour = "black") +
  # Interactive version of facet_wrap.
  # Use labeller_interactive for the interactive strips
  facet_wrap_interactive(vars(group), nrow = 1,
                         labeller = labeller_interactive(
                           aes(tooltip = paste0("Group: ", group), 
                               data_id = group)
                           )
                         ) + 
  # Interactive version of scale_fill_manual
  # Specify he tooltip and data_id attributes for the legend keys
  # Use labeller_interactive for making legend title interactive
  scale_fill_manual_interactive(values = c("#1B9E77", "#D95F02",
                                           "#7570B3", "#E7298A"),
                                name = label_interactive(
                                  "Attributes", 
                                  tooltip = "Interactive legend title", 
                                  data_id =   "legend.title",
                                  onclick = "alert(\"You clicked the legend title.\")"
                                  ),
                                tooltip = function(x) paste0("Attribute: ", x),
                                data_id = function(x) x) + 
  # Interactive elements in the theme
  # Use element_text_interactive for the axis title, axis text and plot title
  theme(legend.position = "top",
        axis.title = element_text_interactive(
          data_id = "axis.title",
          tooltip = "Axis title",
          onclick = "alert(\"You clicked the axis title.\")",
          hover_css = "fill:red;stroke:none;"
        ),
        axis.text = element_text_interactive(
          data_id = "axis.text",
          tooltip = "Axis text",
          onclick = "alert(\"You clicked the axis text\")",
          hover_css = "fill:red;stroke:none;"
        ),
        plot.title = element_text_interactive(
          data_id = "plot.title",
          tooltip = "Plot title",
          onclick = "alert(\"You clicked the plot title\")",
          hover_css = "fill:blue;stroke:black;"
        )) 

girafe(ggobj = gg_obj)

Hover and click over any element in the plot to highlight it and open a dialog box showing additional information.

ggiraph is a very powerful package and the examples presented here in this vignette cover a small subset of features offered by ggiraph. Please see the ggiraph book to learn more about the wonderful plots that can be created using ggiraph.