A filled contour plot displays colored regions between level curves of a 2D scalar field, creating a smooth gradient visualization of continuous data. Unlike basic contour plots that show only isolines, filled contours use color bands to represent value ranges, making it easier to perceive gradual changes and identify regions of similar magnitude. This visualization is particularly effective for showing how a quantity varies continuously across a 2D surface.
#' anyplot.ai
#' contour-filled: Filled Contour Plot
#' Library: ggplot2 3.5.1 | R 4.4.1
#' Quality: 87/100 | Created: 2026-09-04
library(ggplot2)
library(dplyr)
library(ragg)
set.seed(42)
# --- Theme tokens ------------------------------------------------------------
THEME <- Sys.getenv("ANYPLOT_THEME", "light")
PAGE_BG <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
INK <- if (THEME == "light") "#1A1A17" else "#F0EFE8"
INK_SOFT <- if (THEME == "light") "#4A4A44" else "#B8B7B0"
DIV_MID <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
# --- Data --------------------------------------------------------------------
# Classic "peaks" surface: two Gaussian peaks and a saddle-shaped valley,
# a smooth 2D scalar field with a natural zero midpoint (peak vs. valley).
peaks <- function(x, y) {
3 * (1 - x)^2 * exp(-(x^2) - (y + 1)^2) -
10 * (x / 5 - x^3 - y^5) * exp(-x^2 - y^2) -
1 / 3 * exp(-(x + 1)^2 - y^2)
}
grid_axis <- seq(-3, 3, length.out = 80)
surface <- expand.grid(x = grid_axis, y = grid_axis) %>%
mutate(z = peaks(x, y))
# --- Colors --------------------------------------------------------------
# imprint_div (diverging): matte-red -> theme-adaptive midpoint -> blue,
# used because the surface has a meaningful zero midpoint (valley vs. peak).
n_levels <- 12
level_breaks <- pretty(range(surface$z), n = n_levels)
band_colors <- colorRampPalette(c("#AE3030", DIV_MID, "#4467A3"))(length(level_breaks) - 1)
# --- Storytelling: call out the primary peak and valley -------------------
peak_row <- surface[which.max(surface$z), ]
valley_row <- surface[which.min(surface$z), ]
# Offset labels toward the plot center so they stay inside the fixed domain
# regardless of how close the extremum sits to the -3..3 edge.
peak_label_y <- peak_row$y - sign(peak_row$y) * 0.45
valley_label_y <- valley_row$y - sign(valley_row$y) * 0.45
# --- Plot ----------------------------------------------------------------
p <- ggplot(surface, aes(x, y, z = z)) +
geom_contour_filled(breaks = level_breaks) +
geom_contour(breaks = level_breaks, color = INK_SOFT, linewidth = 0.25, alpha = 0.5) +
geom_point(
data = dplyr::bind_rows(peak_row, valley_row), aes(x, y),
inherit.aes = FALSE, shape = 21, size = 2.2, stroke = 0.6,
color = INK, fill = PAGE_BG
) +
annotate("text", x = peak_row$x, y = peak_label_y, label = "Peak",
color = INK, size = 2.8, fontface = "bold") +
annotate("text", x = valley_row$x, y = valley_label_y, label = "Valley",
color = INK, size = 2.8, fontface = "bold") +
scale_fill_manual(
values = band_colors,
guide = guide_legend(reverse = TRUE, title = "Elevation (m)")
) +
coord_fixed(ratio = 1) +
labs(
title = "contour-filled · r · ggplot2 · anyplot.ai",
x = "X Coordinate (km)",
y = "Y Coordinate (km)"
) +
theme_minimal(base_size = 8) +
theme(
plot.background = element_rect(fill = PAGE_BG, color = PAGE_BG),
panel.background = element_rect(fill = PAGE_BG, color = NA),
panel.grid = element_blank(),
panel.border = element_rect(color = INK_SOFT, fill = NA, linewidth = 0.25),
axis.title = element_text(color = INK, size = 10),
axis.text = element_text(color = INK_SOFT, size = 8),
axis.ticks = element_blank(),
plot.title = element_text(color = INK, size = 12),
legend.background = element_rect(fill = PAGE_BG, color = NA),
legend.text = element_text(color = INK_SOFT, size = 8),
legend.title = element_text(color = INK, size = 10),
legend.key = element_rect(fill = PAGE_BG, color = NA),
legend.key.size = unit(0.35, "cm"),
legend.key.spacing.y = unit(1, "pt")
)
# --- Save --------------------------------------------------------------------
ggsave(
filename = sprintf("plot-%s.png", THEME),
plot = p,
device = ragg::agg_png,
width = 6,
height = 6,
units = "in",
dpi = 400
)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/contour-filled/ggplot2/code. Any spec id and library id listed in llms-full.txt fit the same URL shape; every URL below is complete and callable.
{
"spec_id": "contour-filled",
"language": "r",
"library": "ggplot2",
"page": "https://anyplot.ai/contour-filled/r/ggplot2",
"hub": "https://anyplot.ai/contour-filled",
"code_json": "https://api.anyplot.ai/specs/contour-filled/ggplot2/code",
"spec_json": "https://api.anyplot.ai/specs/contour-filled",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/contour-filled/r/ggplot2/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/contour-filled/r/ggplot2/plot-dark.png",
"quality_score": 87.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Filled Contour Plot on anyplot.ai.