A quiver plot displays vector fields using arrows positioned at grid points. Each arrow represents a vector at that location, with direction indicating the vector's angle and length proportional to its magnitude. This visualization reveals flow patterns, gradients, and field structure in two-dimensional data.
#' anyplot.ai
#' quiver-basic: Basic Quiver Plot
#' Library: ggplot2 3.5.1 | R 4.4.1
#' Quality: 92/100 | Created: 2026-07-24
library(ggplot2)
library(dplyr)
library(tidyr)
library(ragg)
set.seed(42)
# --- Theme tokens -------------------------------------------------------
THEME <- Sys.getenv("ANYPLOT_THEME", "light")
PAGE_BG <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
ELEVATED_BG <- if (THEME == "light") "#FFFDF6" else "#242420"
INK <- if (THEME == "light") "#1A1A17" else "#F0EFE8"
INK_SOFT <- if (THEME == "light") "#4A4A44" else "#B8B7B0"
# Imprint sequential cmap (single-polarity: wind speed magnitude)
IMPRINT_SEQ_LOW <- "#009E73"
IMPRINT_SEQ_HIGH <- "#4467A3"
# --- Data: cyclonic wind field around a low-pressure eye ----------------
# Rotational flow (u = -y, v = x) modulated by a radial Gaussian decay so
# speed peaks in a ring around the calm eye and fades toward the outskirts.
# WIND_SCALE converts the unitless rotation field into storm-force m/s so the
# "Cyclonic" framing matches the numbers on the legend (peak ~34 m/s, low-end
# Category 1 hurricane strength).
WIND_SCALE <- 12
grid <- expand_grid(
x = seq(-8, 8, by = 1),
y = seq(-4.5, 4.5, by = 1)
)
wind <- grid %>%
mutate(
radius = sqrt(x^2 + y^2),
decay = exp(-radius^2 / 40),
u = -y * decay * WIND_SCALE,
v = x * decay * WIND_SCALE,
speed = sqrt(u^2 + v^2)
)
# Scale arrow length so the fastest vector spans ~80% of the 1-unit grid
# spacing, keeping neighbouring arrows from overlapping.
arrow_scale <- 0.8 / max(wind$speed)
wind <- wind %>%
mutate(
xend = x + u * arrow_scale,
yend = y + v * arrow_scale
)
# Dashed radial guide marking the ring of peak tangential wind speed, i.e.
# the radius that maximises r * exp(-r^2/40) (found analytically at r = sqrt(20)).
eyewall_radius <- sqrt(20)
eyewall_theta <- seq(0, 2 * pi, length.out = 200)
eyewall <- tibble::tibble(
x = eyewall_radius * cos(eyewall_theta),
y = eyewall_radius * sin(eyewall_theta)
)
# --- Plot ----------------------------------------------------------------
p <- ggplot(wind, aes(x = x, y = y, xend = xend, yend = yend, color = speed)) +
geom_path(
data = eyewall, aes(x = x, y = y), inherit.aes = FALSE,
linetype = "dashed", linewidth = 0.4, color = INK_SOFT, alpha = 0.5
) +
geom_segment(
linewidth = 0.7,
arrow = arrow(length = unit(2, "mm"), type = "closed", angle = 20)
) +
annotate(
"point", x = 0, y = 0,
shape = 21, size = 3, stroke = 1, color = INK_SOFT, fill = PAGE_BG
) +
annotate(
"text", x = 0, y = -0.9, label = "eye",
color = INK_SOFT, size = 2.6, fontface = "italic"
) +
coord_fixed(ratio = 1, expand = TRUE) +
scale_color_gradient(
low = IMPRINT_SEQ_LOW, high = IMPRINT_SEQ_HIGH,
name = "Wind speed (m/s)"
) +
labs(
x = "Distance east of eye (km)",
y = "Distance north of eye (km)",
title = "Cyclonic Wind Field · quiver-basic · r · ggplot2 · anyplot.ai"
) +
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.major = element_line(color = INK_SOFT, linewidth = 0.15, linetype = "dotted"),
panel.grid.minor = element_blank(),
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 = ELEVATED_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),
plot.margin = margin(10, 14, 10, 10)
)
# --- Save ------------------------------------------------------------------
ggsave(
filename = sprintf("plot-%s.png", THEME),
plot = p,
device = ragg::agg_png,
width = 8,
height = 4.5,
units = "in",
dpi = 400
)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/quiver-basic/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": "quiver-basic",
"language": "r",
"library": "ggplot2",
"page": "https://anyplot.ai/quiver-basic/r/ggplot2",
"hub": "https://anyplot.ai/quiver-basic",
"code_json": "https://api.anyplot.ai/specs/quiver-basic/ggplot2/code",
"spec_json": "https://api.anyplot.ai/specs/quiver-basic",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/quiver-basic/r/ggplot2/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/quiver-basic/r/ggplot2/plot-dark.png",
"quality_score": 92.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Basic Quiver Plot on anyplot.ai.