Show nodes as voronoi tiles

Source: R/geom_node_voronoi.R

This geom is equivalent in functionality to ggforce::geom_voronoi_tile() and allows for plotting of nodes as tiles from a voronoi tesselation. As with ggforce::geom_voronoi_tile() it is possible to restrict the size of the tile to a fixed radius, as well as round corners and expand/contract the tile.

geom_node_voronoi(
  mapping = NULL,
  data = NULL,
  position = "identity",
  show.legend = NA,
  bound = NULL,
  eps = 1e-09,
  max.radius = NULL,
  normalize = FALSE,
  asp.ratio = 1,
  expand = 0,
  radius = 0,
  ...
)

Arguments

mapping

Set of aesthetic mappings created by ggplot2::aes() or ggplot2::aes_(). By default x and y are mapped to x and y in the node data and group set to -1.

data

The data to be displayed in this layer. There are three options:

If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot().

A data.frame, or other object, will override the plot data. All objects will be fortified to produce a data frame. See fortify() for which variables will be created.

A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).

position

A position adjustment to use on the data for this layer. This can be used in various ways, including to prevent overplotting and improving the display. The position argument accepts the following:

  • The result of calling a position function, such as position_jitter(). This method allows for passing extra arguments to the position.

  • A string naming the position adjustment. To give the position as a string, strip the function name of the position_ prefix. For example, to use position_jitter(), give the position as "jitter".

  • For more information and other ways to specify the position, see the layer position documentation.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.

bound

The bounding rectangle for the tesselation or a custom polygon to clip the tesselation to. Defaults to NULL which creates a rectangle expanded 10\ vector giving the bounds in the following order: xmin, xmax, ymin, ymax. If supplied as a polygon it should either be a 2-column matrix or a data.frame containing an x and y column.

eps

A value of epsilon used in testing whether a quantity is zero, mainly in the context of whether points are collinear. If anomalous errors arise, it is possible that these may averted by adjusting the value of eps upward or downward.

max.radius

The maximum distance a tile can extend from the point of origin. Will in effect clip each tile to a circle centered at the point with the given radius. If normalize = TRUE the radius will be given relative to the normalized values

normalize

Should coordinates be normalized prior to calculations. If x and y are in wildly different ranges it can lead to tesselation and triangulation that seems off when plotted without ggplot2::coord_fixed(). Normalization of coordinates solves this. The coordinates are transformed back after calculations.

asp.ratio

If normalize = TRUE the x values will be multiplied by this amount after normalization.

expand

A numeric or unit vector of length one, specifying the expansion amount. Negative values will result in contraction instead. If the value is given as a numeric it will be understood as a proportion of the plot area width.

radius

As expand but specifying the corner radius.

...

Other arguments passed on to layer()'s params argument. These arguments broadly fall into one of 4 categories below. Notably, further arguments to the position argument, or aesthetics that are required can not be passed through .... Unknown arguments that are not part of the 4 categories below are ignored.

  • Static aesthetics that are not mapped to a scale, but are at a fixed value and apply to the layer as a whole. For example, colour = "red" or linewidth = 3. The geom's documentation has an Aesthetics section that lists the available options. The 'required' aesthetics cannot be passed on to the params. Please note that while passing unmapped aesthetics as vectors is technically possible, the order and required length is not guaranteed to be parallel to the input data.

  • When constructing a layer using a stat_*() function, the ... argument can be used to pass on parameters to the geom part of the layer. An example of this is stat_density(geom = "area", outline.type = "both"). The geom's documentation lists which parameters it can accept.

  • Inversely, when constructing a layer using a geom_*() function, the ... argument can be used to pass on parameters to the stat part of the layer. An example of this is geom_area(stat = "density", adjust = 0.5). The stat's documentation lists which parameters it can accept.

  • The key_glyph argument of layer() may also be passed on through .... This can be one of the functions described as key glyphs, to change the display of the layer in the legend.

Aesthetics

geom_node_voronoi understand the following aesthetics. Bold aesthetics are automatically set, but can be overwritten.

  • x

  • y

  • alpha

  • colour

  • fill

  • shape

  • size

  • stroke

  • filter

Author

Thomas Lin Pedersen

Examples

require(tidygraph)
gr <- create_notable('meredith') %>%
  mutate(group = sample(letters[1:4], n(), TRUE))

ggraph(gr) +
  geom_node_voronoi(aes(fill = group, colour = group), alpha = 0.3) +
  geom_edge_link(alpha = 0.3) +
  geom_node_point()
#> Using "stress" as default layout


# Use max.radius to make the tesselation more "node"-like
ggraph(gr) +
  geom_node_voronoi(aes(fill = group, colour = group), alpha = 0.3, max.radius = 1) +
  geom_edge_link(alpha = 0.3) +
  geom_node_point()
#> Using "stress" as default layout