geom_geocontour: 2d contours of a geofield
In andrew-MET/harpVis: Visualisation functions for harp.

geom_geocontour

R Documentation

2d contours of a geofield

Description

These functions visualise geofield data as contours in 2D. They are built on top of geom_contour and geom_contour_filled.

They require data frames with a column containing geofields. This would normally be a geolist column, but a standard list column containing geofields will also work.

Smoothing can be achieved by upscaling the data before plotting. This can only be done using an integer scale factor and the methods can be any function that summarises a vector into a single value, for example "mean", "median", "min", "max", or "downsample". Downsampling is simply sampling a pixel within the upscaled pixel - by default this is the centre.

Usage

geom_geocontour(
  mapping = NULL,
  data = NULL,
  position = "identity",
  ...,
  bins = NULL,
  binwidth = NULL,
  breaks = NULL,
  lineend = "butt",
  linejoin = "round",
  linemitre = 10,
  upscale_factor = 1,
  upscale_method = "mean",
  downsample_location = "centre",
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

geom_geocontour_filled(
  mapping = NULL,
  data = NULL,
  position = "identity",
  ...,
  bins = NULL,
  binwidth = NULL,
  breaks = NULL,
  upscale_factor = 1,
  upscale_method = "mean",
  downsample_location = "centre",
  na.rm = 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)`).
`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.
`bins`	Number of contour bins. Overridden by `breaks`.
`binwidth`	The width of the contour bins. Overridden by `bins`.
`breaks`	One of: Numeric vector to set the contour breaks A function that takes the range of the data and binwidth as input and returns breaks as output. A function can be created from a formula (e.g. ~ fullseq(.x, .y)). Overrides `binwidth` and `bins`. By default, this is a vector of length ten with `pretty()` breaks.
`lineend`	Line end style (round, butt, square).
`linejoin`	Line join style (round, mitre, bevel).
`linemitre`	Line mitre limit (number greater than 1).
`upscale_factor`	An integer by which to upscale the data before computing the contours. For example if this is 2, the upscaled grid will have 2 pixels in each direction from the grid before upscaling.
`upscale_method`	The method used for upscaling. See `geo_upscale` for more details.
`downsample_location`	When "downsample" is the chosen method, each pixel in the upscaled field is sampled from a pixel from the original field that is inside the upscaled pixel. The location of that pixel can be one of "bottom_left", "bottom_centre", "bottom_right", "left_centre", "centre", "right_centre", "top_right", "top_centre", "top_left" or "random".
`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()`.

Aesthetics

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

geofield
colour
alpha
group
linetype
linewidth
weight

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

geofield
colour
fill
alpha
group
linetype
linewidth
weight

Computed variables

These are calculated by the 'stat' part of layers and can be accessed with delayed evaluation. The computed variables differ somewhat for contour lines (compbuted by stat_contour()) and contour bands (filled contours, computed by stat_contour_filled()). The variables nlevel and piece are available for both, whereas level_low, level_high, and level_mid are only available for bands. The variable level is a numeric or a factor depending on whether lines or bands are calculated.

after_stat(level)
Height of contour. For contour lines, this is a numeric vector that represents bin boundaries. For contour bands, this is an ordered factor that represents bin ranges.
after_stat(level_low), after_stat(level_high), after_stat(level_mid)
(contour bands only) Lower and upper bin boundaries for each band, as well as the mid point between boundaries.
after_stat(nlevel)
Height of contour, scaled to a maximum of 1.
after_stat(piece)
Contour piece (an integer).