Compute colors for multi-dimensional data. — data

Given a matrix of observation/element rows and variable/measurement columns, compute a color for each row (or group of rows) such that the colors are distinct, and where more-similar colors roughly designate more-similar data rows (or groups of rows).

data_colors(
  data,
  run_umap = TRUE,
  groups = NULL,
  minimal_saturation = 33,
  minimal_lightness = 20,
  maximal_lightness = 80
)

Arguments

data: A matrix whose rows represent elements/observations and columns represent variables/measurements.
run_umap: A boolean specifying whether to run UMAP on the data to convert it to 3D (by default, TRUE). If FALSE, the data matrix must have exactly 3 columns and will be used as-is.
groups: An optional array with an entry per row containing the identifier of the group the row belongs to.
minimal_saturation: Exclude colors whose saturation (hypot(a, b) in CIELAB color space) is less than this value (by default, 33).
minimal_lightness: Exclude colors whose lightnes (l in CIELAB color space) is less than this value (by default, 20).
maximal_lightness: Exclude colors whose lightnes (l in CIELAB color space) is more than this value (by default, 80).

Value

An array with one entry per row, whose names are the matrix rownames, containing the color of each row. If groups was specified, the array will contain one entry per unique group identifier, whose names are the as.character group identifiers, containing the color of each group.

Details

This is intended to provide a "reasonable" set of colors to "arbitrary" data, for use as a convenient default when investigating unknown data sets. It is not meant to replace hand-picked colors tailored for specific data (e.g. using red colors for "bad" rows and green colors for "good" rows).

This ensures all colors are distinct by packing the (visible part) of the CIELAB color space with the needed number of spheres. To assign the colors to the data, it uses UMAP to reduce the data to 3D. It then uses principal component analysis to represent both the chosen colors (3D sphere centers) and the (3D UMAP) data as point clouds with coordinates in the range 0-1, and finally uses a stable matching algorithm to map these point clouds to each other, thereby assigning a color to each data row. If the data is grouped, then the center of gravity of each group is used to generate a color for each group.

Examples

chameleon::data_colors(stackloss)
#>  [1] "#D86544" "#8B262B" "#EF5205" "#818F3F" "#C5699E" "#AF7E42" "#4D966F"
#>  [8] "#3B9B3D" "#967ACB" "#752D7B" "#C95CCC" "#E55573" "#EF3F9F" "#FE3847"
#> [15] "#F517CC" "#8F71F9" "#721BA5" "#2387F9" "#C84DFA" "#3241A5" "#4A8CCA"