R: (More) Flexible Diverging HCL Palettes

divergingx_hcl {colorspace} | R Documentation

## (More) Flexible Diverging HCL Palettes

### Description

Diverging HCL color palettes generated through combination of two fully flexible (and possibly unbalanced) multi-hue sequential palettes.

### Usage

    divergingx_hcl(
      n,
      palette = "Geyser",
      ...,
      fixup = TRUE,
      alpha = 1,
      rev = FALSE,
      h1,
      h2,
      h3,
      c1,
      c2,
      c3,
      l1,
      l2,
      l3,
      p1,
      p2,
      p3,
      p4,
      cmax1,
      cmax2
    )

    divergingx_palettes(palette = NULL, plot = FALSE, n = 7L, ...)

### Arguments

`n` | the number of colors (>= 1) to be in the palette.
`palette` | character with the name (see details).
`...` | arguments passed to `hex`.
`fixup` | logical. Should the color be corrected to a valid RGB value?
`alpha` | numeric vector of values in the range `[0, 1]` for alpha transparency channel (0 means transparent and 1 means opaque).
`rev` | logical. Should the palette be reversed?
`h1` | numeric. Starting hue coordinate.
`h2` | numeric. Center hue coordinate.
`h3` | numeric. Ending hue coordinate.
`c1` | numeric. Chroma coordinate corresponding to `h1`.
`c2` | numeric. Chroma coordinate corresponding to `h2` (if `NA`, set to 0).
`c3` | numeric. Chroma coordinate corresponding to `h3`.
`l1` | numeric. Luminance coordinate corresponding to `h1`.
`l2` | numeric. Luminance coordinate corresponding to `h2`.
`l3` | numeric. Luminance coordinate corresponding to `h3` (if `NA`, `l1` is used).
`p1` | numeric. Power parameter for chroma coordinates in first sequential palette.
`p2` | numeric. Power parameter for luminance coordinates in first sequential palette (if `NA`, `p1` is used).
`p3` | numeric. Power parameter for chroma coordinates in second sequential palette (if `NA`, `p1` is used).
`p4` | numeric. Power parameter for luminance coordinates in second sequential palette (if `NA`, `p3` is used).
`cmax1` | numeric. Maximum chroma coordinate in first sequential palette (not used if `NA`).
`cmax2` | numeric. Maximum chroma coordinate in second sequential palette (if `NA`, `cmax1` is used).
`plot` | logical. Should the selected HCL color palettes be visualized?

### Details

The `divergingx_hcl` function simply calls `sequential_hcl` twice with a prespecified set of hue, chroma, and luminance parameters. This is similar to `diverging_hcl` but allows for more flexibility: `diverging_hcl` employs two single-hue sequential palettes, always uses zero chroma for the neutral/central color, and restricts the chroma/luminance path to be the same in both “arms” of the palette. In contrast, `divergingx_hcl` relaxes this to two full multi-hue palettes that can thus go through a non-gray neutral color (typically light yellow). Consequently, the chroma/luminance paths can be rather unbalanced between the two arms.

With this additional flexibility various diverging palettes suggested by https://ColorBrewer2.org/ and CARTO (https://carto.com/carto-colors/), can be emulated along with the Zissou 1 palette from wesanderson, Cividis from viridis, and Roma from scico.

Available CARTO palettes: ArmyRose, Earth, Fall, Geyser, TealRose, Temps, and Tropic (with Tropic also available in `diverging_hcl`).

Available ColorBrewer.org palettes: PuOr, RdBu, RdGy, PiYG, PRGn, BrBG, RdYlBu, RdYlGn, Spectral.

### Value

A character vector with (s)RGB codings of the colors in the palette.

### References

Zeileis A, Fisher JC, Hornik K, Ihaka R, McWhite CD, Murrell P, Stauffer R, Wilke CO (2020). “colorspace: A Toolbox for Manipulating and Assessing Colors and Palettes.” Journal of Statistical Software, 96(1), 1–49. doi: 10.18637/jss.v096.i01

### See Also

`sequential_hcl`, `diverging_hcl`

### Examples

    ## show emulated CARTO/ColorBrewer.org palettes
    divergingx_palettes(plot = TRUE)

    ## compared to diverging_hcl() the diverging CARTO palettes are typically warmer
    ## but also less balanced with respect to chroma/luminance, see e.g.,
    specplot(divergingx_hcl(7, "ArmyRose"))

[Package colorspace version 2.0-1 Index]