A matrix-based representation of a network or graph where rows and columns represent nodes and cell color indicates the presence or weight of edges between them. This visualization complements node-link diagrams by excelling at revealing clusters, structural patterns, and density in large or dense networks where node-link layouts become cluttered. Reordering nodes by cluster, degree, or community membership exposes block-diagonal structure and makes group boundaries immediately visible.
# anyplot.ai
# heatmap-adjacency: Network Adjacency Matrix Heatmap
# Library: makie 0.21.9 | Julia 1.11.9
# Quality: 88/100 | Created: 2026-09-05
using CairoMakie
using Colors
using Random
Random.seed!(42)
# --- 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"
# Continuous colormap — sequential, single-polarity (collaboration strength)
const ANYPLOT_SEQ = cgrad([colorant"#009E73", colorant"#4467A3"])
# --- Data ---------------------------------------------------------------
# Cross-team collaboration network: employees grouped by team, weight =
# frequency of joint project work. Nodes are pre-ordered by team so the
# within-team block-diagonal structure is immediately visible.
team_names = ["Engineering", "Design", "Sales", "Marketing"]
team_sizes = [9, 6, 7, 8]
n_nodes = sum(team_sizes)
node_team = vcat([fill(i, team_sizes[i]) for i in eachindex(team_sizes)]...)
# Undirected weighted adjacency matrix — both triangles filled symmetrically.
# Absent edges (including the diagonal) stay NaN so they render as a
# distinct background color rather than a low-intensity data color.
collaboration = fill(NaN, n_nodes, n_nodes)
for i in 1:n_nodes, j in (i + 1):n_nodes
same_team = node_team[i] == node_team[j]
connected = same_team ? rand() < 0.75 : rand() < 0.12
if connected
weight = same_team ? 0.55 + rand() * 0.45 : 0.05 + rand() * 0.30
collaboration[i, j] = weight
collaboration[j, i] = weight
end
end
# Group boundaries (between blocks) and centers (for tick labels)
cum_sizes = cumsum(team_sizes)
boundaries = cum_sizes[1:(end - 1)] .+ 0.5
centers = cum_sizes .- team_sizes ./ 2 .+ 0.5
# --- Plot -----------------------------------------------------------------
fig = Figure(
size = (1200, 1200),
fontsize = 14,
backgroundcolor = PAGE_BG,
)
ax = Axis(
fig[1, 1];
title = "heatmap-adjacency · julia · makie · anyplot.ai",
titlesize = 20,
titlecolor = INK,
subtitle = "$(n_nodes) nodes, ordered by team",
subtitlesize = 13,
subtitlecolor = INK_SOFT,
xlabel = "Target",
ylabel = "Source",
xlabelsize = 14,
ylabelsize = 14,
xlabelcolor = INK,
ylabelcolor = INK,
xticks = (centers, team_names),
yticks = (centers, team_names),
xticklabelsize = 13,
yticklabelsize = 13,
xticklabelcolor = INK_SOFT,
yticklabelcolor = INK_SOFT,
xtickcolor = INK_SOFT,
ytickcolor = INK_SOFT,
# Unlabeled per-node minor ticks confirm the true 30x30 node density
# underneath the 4 labeled team blocks.
xminorticksvisible = true,
yminorticksvisible = true,
xminorticks = 0.5:1:(n_nodes + 0.5),
yminorticks = 0.5:1:(n_nodes + 0.5),
xminortickalign = 1,
yminortickalign = 1,
xminortickcolor = INK_SOFT,
yminortickcolor = INK_SOFT,
xminorticksize = 3,
yminorticksize = 3,
backgroundcolor = PAGE_BG,
aspect = DataAspect(),
# Enclosed heatmap grid — style-guide spine exception keeps all 4 sides.
topspinevisible = true,
rightspinevisible = true,
leftspinecolor = INK_SOFT,
bottomspinecolor = INK_SOFT,
topspinecolor = INK_SOFT,
rightspinecolor = INK_SOFT,
xgridvisible = false,
ygridvisible = false,
)
ax.yreversed = true
hm = heatmap!(
ax, collaboration;
colormap = ANYPLOT_SEQ,
colorrange = (0.0, 1.0),
nan_color = PAGE_BG,
)
vlines!(ax, boundaries; color = INK_SOFT, linewidth = 1.5)
hlines!(ax, boundaries; color = INK_SOFT, linewidth = 1.5)
Colorbar(
fig[1, 2], hm;
label = "Collaboration Strength",
labelcolor = INK,
labelsize = 14,
ticklabelcolor = INK_SOFT,
ticklabelsize = 13,
tickcolor = INK_SOFT,
width = 25,
)
colgap!(fig.layout, 20)
# --- Save -------------------------------------------------------------------
save("plot-$(THEME).png", fig; px_per_unit = 2)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/heatmap-adjacency/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": "heatmap-adjacency",
"language": "julia",
"library": "makie",
"page": "https://anyplot.ai/heatmap-adjacency/julia/makie",
"hub": "https://anyplot.ai/heatmap-adjacency",
"code_json": "https://api.anyplot.ai/specs/heatmap-adjacency/makie/code",
"spec_json": "https://api.anyplot.ai/specs/heatmap-adjacency",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/heatmap-adjacency/julia/makie/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/heatmap-adjacency/julia/makie/plot-dark.png",
"quality_score": 88.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Network Adjacency Matrix Heatmap on anyplot.ai.