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.

Usage

geom_curve_dual_function(
  fun,
  xlim = c(-3, 3),
  n = 701,
  curvature = 0,
  angle = 90,
  ncp = 5,
  colour1 = NULL,
  colour2 = NULL,
  base_color = NULL,
  contrast = 4.5,
  method_contrast = "WCAG",
  linewidth = 1.2,
  args = list(),
  smooth = TRUE,
  color1 = NULL,
  color2 = NULL,
  alpha = 1,
  ...
)

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.
colour1, colour2: Fixed top/bottom stroke colours. If only colour1 given, colour2 is derived for contrast. (Aliases color1/color2 also accepted.)
base_color: Optional base color to derive a contrast pair (overrides colour1/colour2 if supplied).
contrast, method_contrast: Passed to adjust_contrast_pair() when deriving colors.
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 TRUE.
color1, color2: U.S.-spelling aliases for colour1/colour2. Identical in effect; prefer colour1/colour2 in code examples.
alpha: Overall opacity for both strokes (0–1).
...: 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",
  linewidth = 1,
  smooth = TRUE
  ) +
  theme_dark()



ggplot() +
  geom_curve_dual_function(
    fun = dnorm,
    xlim = c(-5, 5),
    base_color = "green",
    linewidth = 1,
    smooth = TRUE
  ) +
  geom_curve_dual_function(
    fun = dt,
    args = list(df = 1),
    xlim = c(-5, 5),
    base_color = "brown",
    linewidth = 1,
    smooth = TRUE
  ) +
  theme_dark()