Fortify Spat* Objects — fortify.Spat • tidyterra

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

Note that these methods are now implemented as a wrapper of tidy.Spat methods.

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, ...)

# S3 method for class 'SpatExtent'
fortify(model, data, ..., crs = "")

Arguments

model

A SpatRaster created with terra::rast() or a SpatVector created with terra::vect(). Also support SpatGraticule (see terra::graticule()) and SpatExtent (see terra::ext()).

data

Not used by this method.

...

Ignored by these methods.

.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 provided on long format. When FALSE (the default) it would be provided as a data frame with a column for each layer. See Details.

crs

Input potentially including or representing a CRS. It could be a sf/sfc object, a SpatRaster/SpatVector object, a crs object from sf::st_crs(), a character (for example a proj4 string) or a integer (representing an EPSG code).

Value

fortify.SpatVector(), fortify.SpatGraticule() and fortify.SpatExtent() return a sf object.

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`, `SpatGraticule` and `SpatExtent`

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

Examples

# \donttest{

# Demonstrate the use with ggplot2
library(ggplot2)


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


# You can now use a SpatRaster with any geom
ggplot(r, maxcell = 50) +
  geom_histogram(aes(x = elevation),
    bins = 20, fill = "lightblue",
    color = "black"
  )
#> <SpatRaster> resampled to 56 cells.


# For SpatVector, SpatGraticule and SpatExtent you can use now geom_sf()

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

class(cyl)
#> [1] "SpatVector"
#> attr(,"package")
#> [1] "terra"

ggplot(cyl) +
  geom_sf()


# SpatGraticule
g <- terra::graticule(60, 30, crs = "+proj=robin")

class(g)
#> [1] "SpatGraticule"
#> attr(,"package")
#> [1] "terra"

ggplot(g) +
  geom_sf()


# SpatExtent
ex <- terra::ext(cyl)

class(ex)
#> [1] "SpatExtent"
#> attr(,"package")
#> [1] "terra"

ggplot(ex, crs = cyl) +
  geom_sf(fill = "red", alpha = 0.3) +
  geom_sf(data = cyl, fill = NA)

# }

Fortify `Spat*` Objects