An alluvial diagram visualizes how entities flow or transition between discrete categories across multiple time points or ordered stages. Unlike general Sankey diagrams, alluvial diagrams enforce strict vertical ordering where each column represents a specific time step or category dimension. Bands connect related segments to show how proportions shift over time, making it ideal for tracking structural changes, migrations, and transitions in categorical data.
# anyplot.ai
# alluvial-basic: Basic Alluvial Diagram
# Library: makie 0.21.9 | Julia 1.11.9
# Quality: 90/100 | Created: 2026-09-02
using CairoMakie
using Colors
# --- Theme tokens -------------------------------------------------------------
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"
const INK_MUTED = THEME == "light" ? colorant"#6B6A63" : colorant"#A8A79F"
const IMPRINT_PALETTE = [
colorant"#009E73", # 1 — brand green
colorant"#C475FD", # 2 — lavender
colorant"#4467A3", # 3 — blue
]
# --- Data: academic track transitions across four semesters -------------------
# Undecided is mapped to the theme-adaptive "muted" semantic anchor rather than
# a categorical slot — it literally represents a neutral / uncommitted state.
categories = ["STEM", "Business", "Humanities", "Undecided"]
category_colors = [IMPRINT_PALETTE[1], IMPRINT_PALETTE[2], IMPRINT_PALETTE[3], INK_MUTED]
time_labels = ["Semester 1", "Semester 2", "Semester 3", "Semester 4"]
nt = length(time_labels)
ncat = length(categories)
# values[t, k] — enrolled students in category k at time point t
values = Float64[
140 100 80 60
145 110 95 30
145 113 95 27
146 112 98 24
]
# flows[t][i, j] — students moving from category i (at time t) to category j (at time t+1)
flows = [
Float64[110 15 10 5; 10 70 15 5; 5 10 60 5; 20 15 10 15],
Float64[120 15 5 5; 10 80 15 5; 5 10 70 10; 10 8 5 7],
Float64[130 10 3 2; 8 90 10 5; 3 7 80 5; 5 5 5 12],
]
# --- Layout: stack each column's categories top-to-bottom with a fixed gap ---
gap = 6.0
node_top = zeros(Float64, nt, ncat)
node_bot = zeros(Float64, nt, ncat)
for t in 1:nt
cursor = 0.0
for k in 1:ncat
node_top[t, k] = cursor
node_bot[t, k] = cursor - values[t, k]
cursor = node_bot[t, k] - gap
end
end
node_halfwidth = 0.06
npts = 40
# --- Plot -----------------------------------------------------------------
fig = Figure(
resolution = (1600, 900),
fontsize = 14,
backgroundcolor = PAGE_BG,
figure_padding = (130, 130, 10, 10),
)
ax = Axis(
fig[1, 1];
title = "alluvial-basic · julia · makie · anyplot.ai",
titlesize = 20,
titlecolor = INK,
xticks = (1:nt, time_labels),
xticklabelsize = 16,
xticklabelcolor = INK,
xticksvisible = false,
yticksvisible = false,
yticklabelsvisible = false,
ylabelvisible = false,
xgridvisible = false,
ygridvisible = false,
topspinevisible = false,
rightspinevisible = false,
leftspinevisible = false,
bottomspinecolor = INK_SOFT,
backgroundcolor = PAGE_BG,
)
# Flow bands (drawn first, sit beneath the nodes). Sub-segments within a source
# node are ordered by destination category, and within a destination node by
# source category, so bands never cross their own siblings.
for t in 1:(nt - 1)
out_cursor = copy(node_top[t, :])
in_cursor = copy(node_top[t + 1, :])
for i in 1:ncat, j in 1:ncat
f = flows[t][i, j]
f <= 0 && continue
src_top = out_cursor[i]
src_bot = src_top - f
out_cursor[i] = src_bot
dst_top = in_cursor[j]
dst_bot = dst_top - f
in_cursor[j] = dst_bot
x_left = t + node_halfwidth
x_right = (t + 1) - node_halfwidth
xs = range(x_left, x_right, length = npts)
ease = [(1 - cos(pi * (x - x_left) / (x_right - x_left))) / 2 for x in xs]
ys_top = src_top .+ (dst_top - src_top) .* ease
ys_bot = src_bot .+ (dst_bot - src_bot) .* ease
band_pts = vcat(Point2f.(xs, ys_top), Point2f.(reverse(xs), reverse(ys_bot)))
poly!(ax, band_pts; color = (category_colors[i], 0.55), strokewidth = 0)
end
end
# Nodes (stacked category blocks per time point)
for t in 1:nt, k in 1:ncat
corners = Point2f[
(t - node_halfwidth, node_top[t, k]),
(t + node_halfwidth, node_top[t, k]),
(t + node_halfwidth, node_bot[t, k]),
(t - node_halfwidth, node_bot[t, k]),
]
poly!(ax, corners; color = category_colors[k], strokecolor = PAGE_BG, strokewidth = 2)
end
# Category labels at the first and last column, with enrollment counts
for k in 1:ncat
y_first = (node_top[1, k] + node_bot[1, k]) / 2
text!(ax, 1 - node_halfwidth - 0.04, y_first;
text = "$(categories[k]) ($(Int(values[1, k])))",
align = (:right, :center), color = INK, fontsize = 14)
y_last = (node_top[nt, k] + node_bot[nt, k]) / 2
text!(ax, nt + node_halfwidth + 0.04, y_last;
text = "$(categories[k]) ($(Int(values[nt, k])))",
align = (:left, :center), color = INK, fontsize = 14)
end
xlims!(ax, 1 - 0.9, nt + 0.9)
legend_elems = [PolyElement(color = c) for c in category_colors]
Legend(
fig[2, 1], legend_elems, categories, "Track";
orientation = :horizontal, tellwidth = false, framevisible = false,
labelcolor = INK, titlecolor = INK,
)
rowsize!(fig.layout, 2, Relative(0.08))
# --- Save -----------------------------------------------------------------
save("plot-$(THEME).png", fig; px_per_unit = 2)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/alluvial-basic/makie/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": "alluvial-basic",
"language": "julia",
"library": "makie",
"page": "https://anyplot.ai/alluvial-basic/julia/makie",
"hub": "https://anyplot.ai/alluvial-basic",
"code_json": "https://api.anyplot.ai/specs/alluvial-basic/makie/code",
"spec_json": "https://api.anyplot.ai/specs/alluvial-basic",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/alluvial-basic/julia/makie/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/alluvial-basic/julia/makie/plot-dark.png",
"quality_score": 90.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Basic Alluvial Diagram on anyplot.ai.