Dual-Tone Curved Function Lines — geom_curve_dual

Draws a function (e.g., density or mathematical curve) using perceptually offset dual-stroke curved line segments.

geom_curve_dual_function(
  fun,
  xlim = c(-3, 3),
  n = 701,
  curvature = 0,
  angle = 90,
  ncp = 20,
  color1 = "#FFFFFF",
  color2 = NULL,
  background = "#000000",
  contrast_method = "APCA",
  offset = 0.003,
  linewidth = 1.2,
  args = list(),
  smooth = FALSE,
  ...
)

Arguments

fun: A function to evaluate (e.g., dnorm, dt).
xlim: Range of x-values to evaluate over (numeric vector of length 2).
n: Number of segments to compute (default: 201).
curvature, angle, ncp: Passed to underlying geom_curve_dual segments.
color1: Top stroke color (typically light).
color2: Bottom stroke color (typically dark). If NULL, will be auto-computed for contrast.
background: Background color used for contrast calculation (default: "#000000").
contrast_method: Either "apca", "wcag", or "auto".
offset: Perpendicular offset between strokes.
linewidth: Stroke width for the top line.
args: List of arguments passed to fun (for example, list(df = 1) for dt).
smooth: Use smooth dual-stroke curves (geom_path) instead of segmented curves (geom_curve_dual). Default is FALSE.
...: Additional arguments passed to geom_curve_dual().

Value

A ggplot2 layer with curved segments.

Examples

library(ggplot2)

base <- ggplot() + xlim(-2.05,2.05)
base +
  geom_curve_dual_function(
  fun = function(x) 0.5 * exp(-abs(x)),
  xlim = c(-2, 2),
  color1 = "#EEEEEE",
  color2 = "#222222",
  offset = 0.004,
  linewidth = 1,
  smooth = TRUE
  ) +
  theme_dark()


pair1 <- adjust_contrast_pair("#FFFFFF", background = "black", method = "APCA")
pair2 <- adjust_contrast_pair("#AAAAAA", background = "black", method = "APCA")

ggplot() +
  geom_curve_dual_function(
    fun = dnorm,
    xlim = c(-5, 5),
    color1  = pair1$light,
    color2 = pair1$dark,
    offset = 0.003,
    linewidth = 1,
    smooth = TRUE
  ) +
  geom_curve_dual_function(
    fun = dt,
    args = list(df = 1),
    xlim = c(-5, 5),
    color1  = pair2$light,
    color2 = pair2$dark,
    offset = 0.003,
    linewidth = 1,
    smooth = TRUE
  ) +
  theme_dark()