scale_color_colorplane: Bivariate Color Space Projection Scale

In colorplaner: A 'ggplot2' Extension to Visualize Two Variables per Color Aesthetic Through Color Space Projections

Description

Maps two continuous variables into a single display color, using either the color and color2 aesthetics (scale_color_colorplane) or the fill and fill2 aesthetics (scale_fill_colorplane). Variables mapped to color or fill are be mapped to the horizontal component of the colorplane scale and color/fill2 are mapped to the vertical component.

Usage

scale_color_colorplane(name = waiver(), axis_title = waiver(),
  axis_title_y = waiver(), breaks = waiver(), breaks_y = waiver(),
  labels = waiver(), labels_y = waiver(), limits = NULL,
  limits_y = NULL, color_projection = "YUV", rescaler = rescale,
  oob = censor, trans = "identity", na.color = "black",
  na.value = NA_real_, guide = "colorplane", ...)

scale_fill_colorplane(name = waiver(), axis_title = waiver(),
  axis_title_y = waiver(), breaks = waiver(), breaks_y = waiver(),
  labels = waiver(), labels_y = waiver(), limits = NULL,
  limits_y = NULL, color_projection = "YUV", rescaler = rescale,
  oob = censor, trans = "identity", na.color = "black",
  na.value = NA_real_, guide = "colorplane", ...)

Arguments

name	Character string or expression to be used as guide title. Defaults to "Color Key" or "Fill Color Key" to match the scale function used.
axis_title, axis_title_y	Character strings or expressions indicating the horizontal and vertical axis titles in the guide, respectively. If NULL, the title is not shown. By default (waiver), the name of the scale or the name of the variable mapped to the aesthetic.
breaks	One of: NULL for no breaks waiver() for the default breaks computed by the transformation object A numeric vector of positions A function that takes the limits as input and returns breaks as output
breaks_y	As breaks, but for vertical axis (i.e. color2 or fill2)
labels	One of: NULL for no labels waiver() for the default labels computed by the transformation object A character vector giving labels (must be same length as breaks) A function that takes the breaks as input and returns labels as output
labels_y	As labels, but for vertical axis (i.e. color2 or fill2)
limits	A numeric vector of length two providing limits of the scale. Use NA to refer to the existing minimum or maximum.
limits_y	As limits, but for vertical axis (i.e. color2 or fill2)
color_projection	Projection mapping to use. Either the name of an included projection or a function that performs the projection. See color_projections.
rescaler	Used by diverging and n colour gradients (i.e. scale_colour_gradient2, scale_colour_gradientn). A function used to scale the input values to the range [0, 1].
oob	Function that handles limits outside of the scale limits (out of bounds). The default replaces out of bounds values with NA.
trans	Either the name of a transformation object, or the object itself. Built-in transformations include "asn", "atanh", "boxcox", "exp", "identity", "log", "log10", "log1p", "log2", "logit", "probability", "probit", "reciprocal", "reverse" and "sqrt". A transformation object bundles together a transform, it's inverse, and methods for generating breaks and labels. Transformation objects are defined in the scales package, and are called name_trans, e.g. boxcox_trans. You can create your own transformation with trans_new.
na.color	Character string containing a valid R color to use when plotting missing data or data outside the limits.
na.value	Missing values will be replaced with this value.
guide	Name of guide object, or object itself. Defaults to guide_colorplane designed for this scale. Behavior of other guides with this scale is not defined.
...	Additional arguments to pass on to color_projection function.

Details

Variable values are projected into color space to create a bivariate gradient. The default projection maps values to the U and V components of YUV color space. In the YUV color space, the full spectrum of chrominance (color difference) is encoded into the U and V components and luminosity (brightness) is encoded in the Y component. For a fixed value of Y, the remaining U-V color space is a plane of all possible colors at that brightness. Therefore, mapping data to this projection utilizes the full color spectrum to provide visual discrimination between differing values.

The YUV projection colorplane scale is visually divided into four quadrants: green when both values are small, fuchsia when both are large, orange when the horizontal variable is small and the vertical is large, and blue when the horizontal variable is large and the vertical is small. Values closer to the extremes are saturated and the center of the scale, representing the mid-point of the ranges for both variables, is grey.

Alternative color projections can be used, but may not be as interpretable. See color_projections for information on specifying or creating other color projections.

References

Based on continuous_scale, modified 2016.

Examples

library(ggplot2)
if(requireNamespace("mapproj")) {
  crimes <- data.frame(state = tolower(rownames(USArrests)), USArrests)
  states_map <- map_data("state")
  ggplot(crimes,
         aes(map_id = state, fill = Murder, fill2 = UrbanPop)) +
    geom_map(map = states_map) +
    scale_fill_colorplane() +
    expand_limits(x = states_map$long, y = states_map$lat) +
    coord_map()
 }
# setting upper limit for qsec causes points for higher values to plot
# as na.color (black)
ggplot(mtcars, aes(x = wt, y = mpg, color = qsec, colour2 = hp)) +
  geom_point(size = 4) +
  scale_color_colorplane(limits = c(NA, 18.9))

Example output

Loading required namespace: mapproj

colorplaner documentation built on May 29, 2017, 11:54 a.m.