Filled 2d contours of a 3d surface

Source: R/geom_contour_fill.R, R/stat_contour_fill.R

While ggplot2's geom_contour can plot nice contours, it doesn't work with the polygon geom. This stat makes some small manipulation of the data to ensure that all contours are closed and also computes a new aesthetic int.level, which differs from level (computed by ggplot2::geom_contour) in that represents the value of the z aesthetic inside the contour instead of at the edge. It also computes breaks globally instead of per panel, so that faceted plots have all the same binwidth.

geom_contour_fill(
  mapping = NULL,
  data = NULL,
  stat = "ContourFill",
  position = "identity",
  ...,
  breaks = MakeBreaks(),
  bins = NULL,
  binwidth = NULL,
  proj = NULL,
  proj.latlon = TRUE,
  clip = NULL,
  kriging = FALSE,
  global.breaks = TRUE,
  na.fill = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

stat_contour_fill(
  mapping = NULL,
  data = NULL,
  geom = "polygon",
  position = "identity",
  ...,
  breaks = MakeBreaks(),
  bins = NULL,
  binwidth = NULL,
  global.breaks = TRUE,
  proj = NULL,
  proj.latlon = TRUE,
  clip = NULL,
  kriging = FALSE,
  na.fill = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Arguments

mapping

Set of aesthetic mappings created by aes(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

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)).

stat

The statistical transformation to use on the data for this layer. When using a geom_*() function to construct a layer, the stat argument can be used the override the default coupling between geoms and stats. The stat argument accepts the following:

  • A Stat ggproto subclass, for example StatCount.

  • A string naming the stat. To give the stat as a string, strip the function name of the stat_ prefix. For example, to use stat_count(), give the stat as "count".

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

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.

...

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.

breaks

numeric vector of breaks

bins

Number of evenly spaced breaks.

binwidth

Distance between breaks.

proj

The projection to which to project the contours to. It can be either a projection string or a function to apply to the whole contour dataset.

proj.latlon

Logical indicating if the projection step should project from a cartographic projection to a lon/lat grid or the other way around.

clip

A simple features object to be used as a clip. Contours are only drawn in the interior of this polygon.

kriging

Whether to perform ordinary kriging before contouring. Use this if you want to use contours with irregularly spaced data. If FALSE, no kriging is performed. If TRUE, kriging will be performed with 40 points. If a numeric, kriging will be performed with kriging points.

global.breaks

Logical indicating whether breaks should be computed for the whole data or for each grouping.

na.fill

How to fill missing values.

  • FALSE for letting the computation fail with no interpolation

  • TRUE for imputing missing values with Impute2D

  • A numeric value for constant imputation

  • A function that takes a vector and returns a numeric (e.g. mean)

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.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().

geom

The geometric object to use to display the data for this layer. When using a stat_*() function to construct a layer, the geom argument can be used to override the default coupling between stats and geoms. The geom argument accepts the following:

  • A Geom ggproto subclass, for example GeomPoint.

  • A string naming the geom. To give the geom as a string, strip the function name of the geom_ prefix. For example, to use geom_point(), give the geom as "point".

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

Aesthetics

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

  • x

  • y

  • alpha

  • colour

  • group

  • linetype

  • size

  • weight

Computed variables

level

An ordered factor that represents bin ranges.

level_d

Same as level, but automatically uses scale_fill_discretised()

level_low,level_high,level_mid

Lower and upper bin boundaries for each band, as well the mid point between the boundaries.

Examples


library(ggplot2)
surface <- reshape2::melt(volcano)
ggplot(surface, aes(Var1, Var2, z = value)) +
  geom_contour_fill() +
  geom_contour(color = "black", size = 0.1)
#> Warning: Using `size` aesthetic for lines was deprecated in ggplot2 3.4.0.
#> ℹ Please use `linewidth` instead.


ggplot(surface, aes(Var1, Var2, z = value)) +
  geom_contour_fill(aes(fill = after_stat(level)))


ggplot(surface, aes(Var1, Var2, z = value)) +
  geom_contour_fill(aes(fill = after_stat(level_d)))