color_projections: Color Space Projections

Description

Functions to define how variables are mapped into color space. Used for the color_projection argument to scale_color_colorplane and scale_fill_colorplane. Custom functions can also be defined following this signature.

Usage

YUV_projection(x, y, Y = 0.3)
red_blue_projection(x, y)
interpolate_projection(x, y, zero_color, horizontal_color, vertical_color)

Arguments

x, y

numeric vectors of equal length containing the values to be mapped to the horizontal and vertical axes of the colorplane.

numeric value in range 0 to 1 for the fixed luminosity level in YUV projections.

zero_color, horizontal_color, vertical_color

Character strings specifying R colors to use in interpolation projections. See Details.

Value

Character vector of colors of the same length as x and y.

Details

Color space projection functions take two numeric vectors and return a single character vector of the same length that specifies the colors to plot in the form "#rrggbb", as returned by rgb. Additional projection functions can be defined following the same signature and passed to the color_projection argument of the scale_*_colorplane scale constructors. When writing custom projection functions, expect two arguments that are numeric vectors scaled to a range of 0 to 1 and that do not contain missing values. Custom projections can accept additional arguments that are passed through from the ... of scale_*_colorplane.

For interpolate_projection, a color space is created via linear RGB-space interpolation for each axis and then blending by averages. zero_color is the base color when both x and y are minimal. horizontal_color specified the color to interpolate towards for increasing x values and vertical_color for y. The plotted color will be a simple average of the interpolated x and y values.

References

YUV conversion matrix from https://en.wikipedia.org/wiki/YUV. UV limits sourced from Deveroux VG. Limiting of YUV Video Signals. British Broadcasting System. 1987 .

Examples

Run this code

library(ggplot2)
ggplot(mtcars, aes(x = wt, y = mpg, color = disp, colour2 = hp)) +
  geom_point() +
  scale_color_colorplane(color_projection = interpolate_projection,
                         zero_color = "darkorange2",
                         horizontal_color = "mediumspringgreen",
                         vertical_color = "magenta")

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