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Discrete scales based in the color table of a SpatRaster

Source: R/scales_coltab.R
scale_coltab.Rd

Some categorical SpatRaster objects may have an associated color table. This function extract those values. These functions generates scales and vector of colors based on the color table terra::coltab() associated to a SpatRaster.

You can also get a vector of colors named with the corresponding factor with get_coltab_pal().

Additional parameters ... would be passed on to ggplot2::discrete_scale().

Note that tidyterra just documents a selection of these additional parameters, check ggplot2::discrete_scale() to see the full range of parameters accepted.

Usage

scale_fill_coltab(
  data,
  ...,
  alpha = NA,
  na.translate = FALSE,
  na.value = "transparent",
  drop = TRUE
)

scale_colour_coltab(
  data,
  ...,
  alpha = NA,
  na.translate = FALSE,
  na.value = "transparent",
  drop = TRUE
)

get_coltab_pal(x)

Arguments

data, x

A SpatRaster with one or several color tables. See terra::has.colors().

...

Arguments passed on to ggplot2::discrete_scale

breaks

One of:

  • NULL for no breaks

  • waiver() for the default breaks (the scale limits)

  • A character vector of breaks

  • A function that takes the limits as input and returns breaks as output. Also accepts rlang lambda function notation.

minor_breaks

One of:

  • NULL for no minor breaks

  • waiver() for the default breaks (none for discrete, one minor break between each major break for continuous)

  • A numeric vector of positions

  • A function that given the limits returns a vector of minor breaks. Also accepts rlang lambda function notation. When the function has two arguments, it will be given the limits and major break positions.

labels

One of the options below. Please note that when labels is a vector, it is highly recommended to also set the breaks argument as a vector to protect against unintended mismatches.

  • NULL for no labels

  • waiver() for the default labels computed by the transformation object

  • A character vector giving labels (must be same length as breaks)

  • An expression vector (must be the same length as breaks). See ?plotmath for details.

  • A function that takes the breaks as input and returns labels as output. Also accepts rlang lambda function notation.

limits

One of:

  • NULL to use the default scale values

  • A character vector that defines possible values of the scale and their order

  • A function that accepts the existing (automatic) values and returns new ones. Also accepts rlang lambda function notation.

expand

For position scales, a vector of range expansion constants used to add some padding around the data to ensure that they are placed some distance away from the axes. Use the convenience function expansion() to generate the values for the expand argument. The defaults are to expand the scale by 5% on each side for continuous variables, and by 0.6 units on each side for discrete variables.

alpha

The alpha transparency: could be NA or a number in [0,1]. See argument alpha in scale_fill_terrain_d().

na.translate

Should NA values be removed from the legend? Default is TRUE.

na.value

Missing values will be replaced with this value. By default, tidyterra uses na.value = "transparent" so cells with NA are not filled. See also #120.

drop

Should unused factor levels be omitted from the scale? The default (TRUE) removes unused factors.

Value

The corresponding ggplot2 layer with the values applied to the fill/colour aesthetics.

See also

terra::coltab(), ggplot2::discrete_scale(), ggplot2::scale_fill_manual(),

Examples

library(terra)
# Geological Eras
# Spanish Geological Survey (IGME)

r <- rast(system.file("extdata/cyl_era.tif", package = "tidyterra"))

plot(r)


# Get coltab
coltab_pal <- get_coltab_pal(r)

coltab_pal
#> Precambric-Paleozoic            Paleozoic   Paleozoic-Mesozoic 
#>            "#FFBFE9"            "#9ADDCF"            "#D79EBD" 
#>             Mesozoic    Mesozoic-Cenozoic             Cenozoic 
#>            "#A4FF74"            "#FFD480"            "#FFFFBF" 
#>         Undetermined 
#>            "#FFFFFF" 

# \donttest{
# With ggplot2 + tidyterra
library(ggplot2)

gg <- ggplot() +
  geom_spatraster(data = r)


# Default plot
gg


# With coltabs
gg +
  scale_fill_coltab(data = r)
#> Scale for fill is already present.
#> Adding another scale for fill, which will replace the existing scale.

# }