make_color_pal: Make a color palette.

In ciftiTools: Tools for Reading, Writing, Viewing and Manipulating CIFTI Files

Make a color palette.

Description

Control the mapping of values to colors with colors, color_mode, and zlim.

Usage

make_color_pal(
  colors = NULL,
  color_mode = c("sequential", "qualitative", "diverging"),
  zlim = NULL
)

Arguments

colors	(Optional) "ROY_BIG_BL", the name of a ColorBrewer palette (see RColorBrewer::brewer.pal.info and colorbrewer2.org), the name of a viridisLite palette, or a character vector of colors. NULL (default) will use "ROY_BIG_BL" if color_mode is "sequential" or "diverging", and "Set2" if color_mode is "qualitative". See the description for more details.
color_mode	(Optional) "sequential", "qualitative", or "diverging". Default: "sequential". See the description for more details.
zlim	(Optional) Controls the mapping of values to each color in colors. See the description for more details.

Details

There are three kinds of arguments for colors: "ROY_BIG_BL", the name of a ColorBrewer palette (see RColorBrewer::brewer.pal.info and colorbrewer2.org), the name of a viridisLite palette, or a character vector of color names.

If colors=="ROY_BIG_BL", the "ROY_BIG_BL" palette will be used. It is the same palette as the default for the Connectome Workbench application (https://github.com/Washington-University/workbench/blob/master/src/Files/PaletteFile.cxx). The midpoint will be colored black. From the midpoint toward the upper bound, colors will proceed from black to red to yellow. From the midpoint toward the lower bound, colors will proceed from black to blue to purple to green to aqua. Here is how each color mode behaves if colors=="ROY_BIG_BL":

color_mode=="sequential"

Only half of the palette will be used. If zlim is length 2, the higher value will be the maximum and the lower value will be the minimum. Set zlim[1] > zlim[2] to reverse the color scale. (Note that the second half, black –> red –> yellow, is used by default. To use the negative half specify colors=="ROY_BIG_BL_neg" instead. It will also be used automatically by xifti_read_surface when the data range is negative.) zlim can also be length 10, in which case each value corresponds to the position of an individual color in the half palette.

color_mode=="qualitative"

"ROY_BIG_BL" is not recommended for qualitative data, so a warning will be issued. Palette colors will be selected from the landmark "ROY_BIG_BL" colors, with interpolated colors added if the number of colors in the palette (18) is less than this range. zlim should be a single number: the number of unique colors to get.

color_mode=="diverging"

If zlim is length 2 or 3, the lowest number will be the lower bound and the highest number will be the upper bound. If zlim is length 3, the middle number will be the midpoint (black). The lower and upper bounds will be aqua and yellow, respectively, except if zlim is in descending order, in which case the color scale will be reversed (lowest is yellow; highest is aqua). zlim can also be length 19, in which case each value corresponds to the position of an individual color in the palette.

If colors is the name of an RColorBrewer palette (see RColorBrewer::brewer.pal.info) or viridisLite palette, the colors in that palette will be used, and the following behavior applies. If colors is a character vector of color names (hex codes or standard R color names), the following behavior applies directly:

color_mode=="sequential"

If zlim is length 2, the higher value will be the maximum and the lower value will be the minimum. Set zlim[1] > zlim[2] to reverse the color scale. zlim can also be the same length as the palette, in which case each value corresponds to the position of an individual color in the palette.

color_mode=="qualitative"

zlim should be a single number: the number of unique colors to get. Color interpolation will be used if the number of colors in the palette is less than this range. If length(zlim)==length(colors), each color will be mapped to each corresponding value.

color_mode=="diverging"

If zlim is length 2 or 3, the lowest number will be the lower bound and the highest number will be the upper bound. If zlim is length 3, the middle number will be the midpoint. Set zlim in descending order to reverse the color scale. zlim can also be the same length as the palette, in which case each value corresponds to the position of an individual color in the palette.

Value

A data.frame with two columns: "color" (character: color hex codes) and "value" (numeric)

See Also

Other coloring: ROY_BIG_BL(), expand_color_pal(), use_color_pal()

ciftiTools documentation built on Oct. 4, 2024, 1:12 a.m.