Create the `split-heat' colour scheme

This function creates the `split-heat' colour scheme. For a user-defined range (zlim) that spans a `splitting' value (i.e., split = 0), the function returns a dichotomous vector of colours that distinguishes values either side of that value. By default, blue colours are returned for values below split (e.g., negative numbers) and red colours are returned for values above split (e.g., positive numbers).

pretty_cols_split_heat(
  zlim,
  split = 0,
  scheme_cold = "Blues",
  scheme_hot = "Reds",
  select_cold = 1:8,
  select_hot = 1:8,
  n_breaks = 100
)

Arguments

zlim	A numeric range that the colour scheme should span.
split	A number that divides the colour scheme. The default is split = 0, which splits the colour scheme around 0.
scheme_cold	A character that defines the colour scheme for numbers below split (e.g., negative numbers), supported by brewer.pal.
scheme_hot	A character that defines the colour scheme for numbers above split (e.g., positive numbers), supported by brewer.pal.
select_cold, select_hot	Integer vectors that define which colours to draw from scheme_cold and scheme_cold respectively.
n_breaks	The number of breaks in the colour scheme.

Value

The function returns a named list that contains the z limits (`zlim'), a numeric vector of breaks (`breaks') and the associated vector of colours (`col'). This can be passed to image.plot.

Details

This function is designed to work in conjunction with image.plot.

See also

pretty_cols_brewer

Author

Edward Lavender

Examples

# Generate a raster with positive and negative numbers
nrw <- ncol <- 5
n <- nrw * ncol
zlim <- c(-0.1, 0.1)
m <- matrix(runif(n, zlim[1], zlim[2]), nrow = nrw, ncol = ncol)
r <- raster::raster(m)
# Define colours
col_param <- pretty_cols_split_heat(zlim = zlim, n_breaks = 100)
# Visualise raster with colour scheme
fields::image.plot(r,
                   zlim = col_param$zlim,
                   breaks = col_param$breaks,
                   col = col_param$col)