fortify.Spat: Fortify Spat* Objects
In tidyterra: 'tidyverse' Methods and 'ggplot2' Helpers for 'terra' Objects

fortify.Spat

R Documentation

Fortify `⁠Spat*⁠` Objects

Description

Fortify SpatRaster and SpatVector objects to data frames. This provide native compatibility with ggplot2::ggplot().

Usage

## S3 method for class 'SpatRaster'
fortify(
  model,
  data,
  ...,
  .name_repair = "unique",
  maxcell = terra::ncell(model) * 1.1,
  pivot = FALSE
)

## S3 method for class 'SpatVector'
fortify(model, data, ...)

## S3 method for class 'SpatGraticule'
fortify(model, data, ...)

Arguments

`model`	A `SpatRaster` created with `terra::rast()` or a `SpatVector` created with `terra::vect()`.
`data`	Not used by this method.
`...`	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.
`.name_repair`	Treatment of problematic column names: `"minimal"`: No name repair or checks, beyond basic existence. `"unique"`: Make sure names are unique and not empty. `"check_unique"`: (default value), no name repair, but check they are `unique`. `"universal"`: Make the names `unique` and syntactic. a function: apply custom name repair (e.g., `.name_repair = make.names` for names in the style of base R). A purrr-style anonymous function, see `rlang::as_function()`.
`maxcell`	positive integer. Maximum number of cells to use for the plot.
`pivot`	Logical. When `TRUE` the `SpatRaster` would be fortified on long format. When `FALSE` (the default) it would be fortified as a data frame with a column for each layer. See Details.

Value

fortify.SpatVector() returns a sf object and fortify.SpatRaster() returns a tibble. See Methods.

Methods

Implementation of the generic ggplot2::fortify() method.

`SpatRaster`

Return a tibble than can be used with ⁠ggplot2::geom_*⁠ like ggplot2::geom_point(), ggplot2::geom_raster(), etc.

The resulting tibble includes the coordinates on the columns ⁠x, y⁠. The values of each layer are included as additional columns named as per the name of the layer on the SpatRaster.

The CRS of the SpatRaster can be retrieved with attr(fortifiedSpatRaster, "crs").

It is possible to convert the fortified object onto a SpatRaster again with as_spatraster().

When pivot = TRUE the SpatRaster is fortified in a "long" format (see tidyr::pivot_longer()). The fortified object would have the following columns:

⁠x,y⁠: Coordinates (center) of the cell on the corresponding CRS.
lyr: Indicating the name of the SpatRaster layer of value.
value: The value of the SpatRaster in the corresponding lyr.

This option may be useful when using several ⁠geom_*⁠ and for faceting, see Examples.

`SpatVector` and `SpatGraticule`

Return a sf object than can be used with ggplot2::geom_sf().

Examples



# Get a SpatRaster
r <- system.file("extdata/volcano2.tif", package = "tidyterra") %>%
  terra::rast() %>%
  terra::project("EPSG:4326")

fortified <- ggplot2::fortify(r)

fortified

# The crs is an attribute of the fortified SpatRaster

attr(fortified, "crs")

# Back to a SpatRaster with
as_spatraster(fortified)

# You can now use a SpatRaster with any geom
library(ggplot2)

ggplot(r) +
  geom_histogram(aes(x = elevation),
    bins = 20, fill = "lightblue",
    color = "black"
  )


# Create a SpatVector
extfile <- system.file("extdata/cyl.gpkg", package = "tidyterra")
cyl <- terra::vect(extfile)

cyl

# To sf
ggplot2::fortify(cyl)

# Now you can use geom_sf() straight away thanks to fortify::SpatVector()

library(ggplot2)

ggplot(cyl) +
  geom_sf()

tidyterra documentation built on April 15, 2025, 1:15 a.m.