geom_interpolate_tern {ggtern}

Ternary Interpolation

Description

This is the heavily requested geometry for interpolating between ternary values, results being rendered using contours on a ternary mesh.

Usage

geom_interpolate_tern(
  mapping = NULL,
  data = NULL,
  stat = "InterpolateTern",
  position = "identity",
  ...,
  method = "auto",
  formula = value ~ poly(x, y, degree = 1),
  lineend = "butt",
  linejoin = "round",
  linemitre = 1,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

stat_interpolate_tern(
  mapping = NULL,
  data = NULL,
  geom = "interpolate_tern",
  position = "identity",
  ...,
  method = "auto",
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  n = 80,
  formula = value ~ poly(x, y, degree = 1),
  base = "ilr"
)

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)).

position

Position adjustment, either as a string naming the adjustment (e.g. "jitter" to use position_jitter), or the result of a call to a position adjustment function. Use the latter if you need to change the settings of the adjustment.

...

Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

method

Smoothing method (function) to use, accepts either NULL or a character vector, e.g. "lm", "glm", "gam", "loess" or a function, e.g. MASS::rlm or mgcv::gam, stats::lm, or stats::loess. "auto" is also accepted for backwards compatibility. It is equivalent to NULL.

For method = NULL the smoothing method is chosen based on the size of the largest group (across all panels). stats::loess() is used for less than 1,000 observations; otherwise mgcv::gam() is used with formula = y ~ s(x, bs = "cs") with method = "REML". Somewhat anecdotally, loess gives a better appearance, but is O(N^{2}) in memory, so does not work for larger datasets.

If you have fewer than 1,000 observations but want to use the same gam() model that method = NULL would use, then set ⁠method = "gam", formula = y ~ s(x, bs = "cs")⁠.

formula

Formula to use in smoothing function, eg. y ~ x, y ~ poly(x, 2), y ~ log(x). NULL by default, in which case method = NULL implies formula = y ~ x when there are fewer than 1,000 observations and formula = y ~ s(x, bs = "cs") otherwise.

lineend

Line end style (round, butt, square).

linejoin

Line join style (round, mitre, bevel).

linemitre

Line mitre limit (number greater than 1).

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

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, stat

Use to override the default connection between geom_smooth() and stat_smooth().

n

number of grid points in each direction

base

the base transformation of the data, options include 'identity' (ie direct on the cartesian space), or 'ilr' which means to use the isometric log ratio transformation.

Aesthetics

geom_InterpolateTernunderstands the following aesthetics (required aesthetics are in bold):

• x

• y

• alpha

• colour

• linetype

• size

Author(s)

Nicholas Hamilton

Examples

data(Feldspar)
ggtern(Feldspar,aes(Ab,An,Or,value=T.C)) + 
stat_interpolate_tern(geom="polygon",
                     formula=value~x+y,
                     method=lm,n=100,
                     breaks=seq(0,1000,by=100),
                     aes(fill=..level..),expand=1) +
                     geom_point()