A chord diagram displays relationships or flows between entities arranged around a circle's perimeter. Arcs (chords) connect related entities, with chord width proportional to the flow magnitude. This visualization excels at revealing the overall structure of connections and identifying the strongest relationships within a system.
# anyplot.ai
# chord-basic: Basic Chord Diagram
# Library: makie 0.22.10 | Julia 1.11.9
# Quality: 90/100 | Created: 2026-06-17
using CairoMakie
using Colors
# --- Theme tokens (see prompts/default-style-guide.md "Theme-adaptive Chrome") ---
const THEME = get(ENV, "ANYPLOT_THEME", "light")
const PAGE_BG = THEME == "light" ? colorant"#FAF8F1" : colorant"#1A1A17"
const INK = THEME == "light" ? colorant"#1A1A17" : colorant"#F0EFE8"
const INK_SOFT = THEME == "light" ? colorant"#4A4A44" : colorant"#B8B7B0"
# Imprint palette — one distinct hue per region; first series is brand green.
const IMPRINT_PALETTE = [
colorant"#009E73", # 1 — brand green
colorant"#C475FD", # 2 — lavender
colorant"#4467A3", # 3 — blue
colorant"#BD8233", # 4 — ochre
colorant"#2ABCCD", # 6 — cyan
colorant"#954477", # 7 — rose
]
# --- Data: annual migration flows between 6 world regions (thousands of people) ---
regions = ["Africa", "Asia", "Europe", "N. America", "S. America", "Oceania"]
# flow[i, j] = migrants moving from region i to region j (diagonal is unused)
flow = Float64[
0 320 410 180 60 40 # from Africa
280 0 520 640 110 240 # from Asia
150 300 0 430 120 160 # from Europe
90 210 260 0 300 80 # from N. America
70 90 140 350 0 30 # from S. America
20 60 90 70 20 0 # from Oceania
]
# --- Geometry: one arc per region, sized by total throughput (outflow + inflow) ---
# Each arc reserves a separate foot for every directed flow, so i→j and j→i render
# as two distinct, source-tinted chords rather than a single merged ribbon.
n = length(regions)
gap = deg2rad(4.0) # angular gap between adjacent arcs
throughput = vec(sum(flow, dims = 2)) .+ vec(sum(flow, dims = 1)) # row + column totals
span = (2π - n * gap) .* throughput ./ sum(throughput)
# Each arc starts at the top (π/2) offset by the spans and gaps that precede it.
arc_start = [π / 2 + sum(span[1:i-1]) + (i - 1) * gap for i in 1:n]
arc_stop = arc_start .+ span
# Walk each arc once, laying down an outgoing foot then an incoming foot per partner.
out_foot = fill((0.0, 0.0), n, n) # out_foot[i, j] = sub-arc on i carrying flow i→j
in_foot = fill((0.0, 0.0), n, n) # in_foot[i, j] = sub-arc on i receiving flow j→i
for i in 1:n
a = arc_start[i]
for j in 1:n
w_out = flow[i, j] / throughput[i] * span[i]
out_foot[i, j] = (a, a + w_out)
a += w_out
w_in = flow[j, i] / throughput[i] * span[i]
in_foot[i, j] = (a, a + w_in)
a += w_in
end
end
# Radii: colored ring sits between r_in and r_out; ribbons attach at r_in.
r_in = 0.90
r_out = 1.00
# Helpers: a point on a circle, and a quadratic Bézier bowed through the centre.
on_ring = (t, rad) -> Point2f(rad * cos(t), rad * sin(t))
bezier = (p0, p2) -> [Point2f((1 - t)^2 * p0[1] + t^2 * p2[1],
(1 - t)^2 * p0[2] + t^2 * p2[2]) for t in range(0, 1; length = 48)]
# --- Plot ---
fig = Figure(size = (1200, 1200), backgroundcolor = PAGE_BG)
ax = Axis(
fig[1, 1];
title = "chord-basic · julia · makie · anyplot.ai",
titlesize = 30,
titlecolor = INK,
titlegap = 16,
backgroundcolor = PAGE_BG,
aspect = DataAspect(),
)
hidespines!(ax)
hidedecorations!(ax)
limits!(ax, -1.5, 1.5, -1.5, 1.5)
# One ribbon per directed flow, tinted by its source. Largest flows are drawn
# first so the thin tail flows stay readable on top, keeping the core legible.
order = sort([(i, j) for i in 1:n, j in 1:n if flow[i, j] > 0];
by = ij -> flow[ij[1], ij[2]], rev = true)
for (i, j) in order
a0, a1 = out_foot[i, j] # source foot on region i
b0, b1 = in_foot[j, i] # target foot on region j
foot_i = [on_ring(t, r_in) for t in range(a0, a1; length = 12)]
foot_j = [on_ring(t, r_in) for t in range(b0, b1; length = 12)]
ribbon = vcat(
foot_i,
bezier(foot_i[end], foot_j[1]),
foot_j,
bezier(foot_j[end], foot_i[1]),
)
poly!(ax, ribbon; color = (IMPRINT_PALETTE[i], 0.5), strokewidth = 0)
end
# Colored arc segment per region (outer ring forward, inner ring back).
for i in 1:n
ang = range(arc_start[i], arc_stop[i]; length = 64)
outer = [on_ring(t, r_out) for t in ang]
inner = [on_ring(t, r_in) for t in reverse(ang)]
poly!(ax, vcat(outer, inner);
color = IMPRINT_PALETTE[i], strokecolor = PAGE_BG, strokewidth = 2)
end
# Region labels, placed just outside the ring and anchored by quadrant.
for i in 1:n
mid = (arc_start[i] + arc_stop[i]) / 2
cx, cy = cos(mid), sin(mid)
ha = abs(cx) < 0.35 ? :center : (cx > 0 ? :left : :right)
va = abs(cy) < 0.35 ? :center : (cy > 0 ? :bottom : :top)
text!(ax, 1.05 * cx, 1.05 * cy;
text = regions[i], align = (ha, va), color = INK,
fontsize = 24, font = :bold)
end
# Footnote: clarify the encoding without faking interactivity.
text!(ax, 0.0, -1.28;
text = "Arc width ∝ total flow · each ribbon is one direction, tinted by its source region",
align = (:center, :bottom), color = INK_SOFT, fontsize = 17)
# --- Save ---
save("plot-$(THEME).png", fig; px_per_unit = 2)
Part of Basic Chord Diagram on anyplot.ai.