GeomHinton: Hinton diagrams for ggplot2

Description

geom_hinton() draws a Hinton diagram: a grid of squares whose area is proportional to the magnitude of each value. For signed data, positive values are shown as white squares and negative values as black squares on a grey background. For unsigned (non-negative) data the background is omitted and squares are drawn in black.

Usage

geom_hinton(
  mapping = NULL,
  data = NULL,
  stat = "hinton",
  position = "identity",
  ...,
  scale_by = c("panel", "global"),
  background = TRUE,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)
stat_hinton(
  mapping = NULL,
  data = NULL,
  geom = "hinton",
  position = "identity",
  ...,
  scale_by = c("panel", "global"),
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Value

A ggplot2 layer that can be added to a ggplot2::ggplot() object.

Arguments

mapping: Set of aesthetic mappings created by ggplot2::aes().
data: The data to be displayed in this layer.
stat: The statistical transformation to use. For geom_hinton() the default is "hinton".
position: Position adjustment.
...: Other arguments passed on to ggplot2::layer().
scale_by: "panel" (default) normalises each panel independently so the largest value in a panel fills its cell. "global" uses the largest value across all panels, enabling cross-panel magnitude comparison.
background: Logical. Draw a grey background rectangle for signed data? Default TRUE. Set to FALSE to suppress the background.
na.rm: If TRUE, rows where weight is NA are silently dropped before computing square sizes. If FALSE (default), they are dropped without a warning (ggplot2 will not render rectangles whose required aesthetics are NA).
show.legend: Logical. Should this layer be included in the legend?
inherit.aes: If FALSE, overrides the default aesthetics rather than combining with them.
geom: The geometric object to use when drawing. For stat_hinton() the default is "hinton".

Aesthetics

geom_hinton() understands the following aesthetics (required aesthetics are in bold):

x: column position (numeric or factor)
y: row position (numeric or factor)
weight: the value to display; determines square size and colour
alpha
colour (border colour; NA by default, no border)
fill (overrides the automatic sign-based colour)
linewidth
linetype

Computed variables

stat_hinton() adds the following columns to the data:

xmin, xmax, ymin, ymax: Rectangle bounds for each square.
fill: "positive", "negative", or "unsigned".
hinton_signed: Logical; TRUE when the panel contains any negative values. Read by GeomHinton to decide whether to draw the grey background (after scale_fill_hinton() has already replaced the fill labels, making fill == "negative" checks unreliable).
cell_w, cell_h: Inferred cell spacing used to size the background.

Aspect ratio

For squares to appear as squares on screen, add coord_fixed() to your plot. Without it, the cells may appear rectangular if the plot's x and y axes have different scales.

Examples

Run this code

library(ggplot2)
m <- matrix(c(0.8, -0.3, 0.5, -0.9, 0.1, 0.6, 0.4, -0.7, 0.2), 3, 3)
df <- matrix_to_hinton(m)

ggplot(df, aes(x = col, y = row, weight = weight)) +
  geom_hinton() +
  scale_fill_hinton() +
  coord_fixed() +
  theme_hinton()

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