feat(matplotlib): implement network-force-directed

Regen from quality 85. Addressed:
- Canvas fixed to figsize=(8,4.5) dpi=400 (3200×1800 px); was 16×9 @300dpi (4800×2700)
- Removed bbox_inches="tight" from savefig (was causing canvas drift)
- Font sizes corrected for 3200×1800 canvas: title 12pt, legend 8pt, hub labels 8pt, footer 8pt
- Node scatter sizes scaled down proportionally (80–200 pt²; was 450–1000 pt²)
- Added visual differentiation: intra-community edges solid/subtle, bridge edges dashed/INK_MUTED
- Fixed palette comment from Okabe-Ito to Imprint palette
- Added pathlib OUTPUT_DIR (__file__-relative) to avoid naming conflict when run from repo root

Author: github-actions[bot]

plots/network-force-directed/implementations/python/matplotlib.py

@@ -1,16 +1,19 @@
-""" anyplot.ai
+"""anyplot.ai
 network-force-directed: Force-Directed Graph
-Library: matplotlib 3.10.9 | Python 3.14.4
-Quality: 85/100 | Updated: 2026-04-26
+Library: matplotlib | Python
 """
 
 import os
+import pathlib
 
 import matplotlib.pyplot as plt
 import numpy as np
 from matplotlib.collections import LineCollection
 
 
+OUTPUT_DIR = pathlib.Path(__file__).parent
+
+
 # Theme tokens (see prompts/default-style-guide.md)
 THEME = os.getenv("ANYPLOT_THEME", "light")
 PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
@@ -19,44 +22,41 @@
 INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
 INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
 
-# Okabe-Ito palette — first series is always #009E73
+# Imprint palette — first series is always #009E73
 COMMUNITY_COLORS = ["#009E73", "#C475FD", "#4467A3"]
 COMMUNITY_NAMES = ["Engineering", "Marketing", "Sales"]
 
-# Data: a 50-person company social network with 3 departments
+# Data: 50-person company social network with 3 departments
 np.random.seed(42)
 community_sizes = [18, 17, 15]
 
 nodes = []
-node_id = 0
+nid_counter = 0
 for comm_idx, size in enumerate(community_sizes):
     for _ in range(size):
-        nodes.append({"id": node_id, "community": comm_idx})
-        node_id += 1
+        nodes.append({"id": nid_counter, "community": comm_idx})
+        nid_counter += 1
 
-edges = []
-# Intra-community edges (dense connections within departments)
+intra_edges = []
 ranges = [(0, 18), (18, 35), (35, 50)]
 for start, stop in ranges:
     for i in range(start, stop):
         for j in range(i + 1, stop):
             if np.random.random() < 0.3:
-                edges.append((i, j))
+                intra_edges.append((i, j))
 
-# Inter-community edges (sparse bridges between departments)
+# Sparse cross-department bridge edges
 bridge_edges = [(0, 18), (5, 20), (10, 25), (18, 35), (22, 40), (30, 45), (8, 38), (15, 48)]
-edges.extend(bridge_edges)
+all_edges = intra_edges + bridge_edges
 
 # Force-directed layout (Fruchterman-Reingold)
 n = len(nodes)
 positions = np.random.rand(n, 2) * 2 - 1
 k = 0.5
-iterations = 200
 
-for iteration in range(iterations):
+for iteration in range(200):
     displacement = np.zeros((n, 2))
 
-    # Repulsive forces between all node pairs
     for i in range(n):
         for j in range(i + 1, n):
             diff = positions[i] - positions[j]
@@ -65,96 +65,96 @@
             displacement[i] += repulsive_force
             displacement[j] -= repulsive_force
 
-    # Attractive forces along edges
-    for src, tgt in edges:
+    for src, tgt in all_edges:
         diff = positions[src] - positions[tgt]
         dist = max(np.linalg.norm(diff), 0.01)
         attractive_force = (dist * dist / k) * (diff / dist)
         displacement[src] -= attractive_force
         displacement[tgt] += attractive_force
 
-    # Apply displacement with cooling
-    temperature = 1 - iteration / iterations
+    temperature = 1 - iteration / 200
     for i in range(n):
         disp_norm = np.linalg.norm(displacement[i])
         if disp_norm > 0:
             positions[i] += (displacement[i] / disp_norm) * min(disp_norm, 0.15 * temperature)
 
-# Normalize positions to [0.08, 0.92] for comfortable margins
 pos_min = positions.min(axis=0)
 pos_max = positions.max(axis=0)
 positions = (positions - pos_min) / (pos_max - pos_min + 1e-6) * 0.84 + 0.08
 pos = {node["id"]: positions[i] for i, node in enumerate(nodes)}
 
-# Node degrees
 degrees = {node["id"]: 0 for node in nodes}
-for src, tgt in edges:
+for src, tgt in all_edges:
     degrees[src] += 1
     degrees[tgt] += 1
 
-# Plot
-fig, ax = plt.subplots(figsize=(16, 9), facecolor=PAGE_BG)
+# Canvas: 3200×1800 px (landscape 16:9)
+fig, ax = plt.subplots(figsize=(8, 4.5), dpi=400, facecolor=PAGE_BG)
 ax.set_facecolor(PAGE_BG)
 
-# Edges (behind nodes), theme-adaptive low-contrast color
-edge_lines = [[(pos[src][0], pos[src][1]), (pos[tgt][0], pos[tgt][1])] for src, tgt in edges]
-lc = LineCollection(edge_lines, colors=INK_SOFT, linewidths=1.5, alpha=0.30, zorder=1)
-ax.add_collection(lc)
+# Intra-community edges (solid, subtle — dense within-team connections)
+intra_lines = [(pos[src], pos[tgt]) for src, tgt in intra_edges]
+lc_intra = LineCollection(intra_lines, colors=INK_SOFT, linewidths=0.7, alpha=0.22, zorder=1)
+ax.add_collection(lc_intra)
+
+# Bridge edges (dashed, more visible — sparse cross-team connections reveal structure)
+bridge_lines = [(pos[src], pos[tgt]) for src, tgt in bridge_edges]
+lc_bridge = LineCollection(bridge_lines, colors=INK_MUTED, linewidths=1.2, alpha=0.65, linestyle="dashed", zorder=1)
+ax.add_collection(lc_bridge)
 
 # Nodes sized by degree
 node_sizes = {}
 for node in nodes:
     x, y = pos[node["id"]]
     degree = degrees[node["id"]]
-    size = 450 + degree * 120
+    size = 80 + degree * 12
     node_sizes[node["id"]] = size
     color = COMMUNITY_COLORS[node["community"]]
-    ax.scatter(x, y, s=size, c=color, edgecolors=PAGE_BG, linewidths=2.0, alpha=0.92, zorder=2)
+    ax.scatter(x, y, s=size, c=color, edgecolors=PAGE_BG, linewidths=1.2, alpha=0.92, zorder=2)
 
-# Label top 2 hubs per community, with size-aware offset to prevent overlap
+# Label top 2 hubs per community
 top_hubs = []
 for comm_idx in range(3):
     comm_degrees = [(node["id"], degrees[node["id"]]) for node in nodes if node["community"] == comm_idx]
     comm_degrees.sort(key=lambda x: x[1], reverse=True)
-    top_hubs.extend([node_id for node_id, _ in comm_degrees[:2]])
+    top_hubs.extend([nid for nid, _ in comm_degrees[:2]])
 
 for node in nodes:
-    node_id = node["id"]
-    if node_id in top_hubs:
-        x, y = pos[node_id]
-        # Offset scales with marker radius (s is area in pt²)
-        offset = 0.012 + 0.0009 * np.sqrt(node_sizes[node_id])
+    nid = node["id"]
+    if nid in top_hubs:
+        x, y = pos[nid]
+        offset = 0.008 + 0.0007 * np.sqrt(node_sizes[nid])
         team_initial = COMMUNITY_NAMES[node["community"]][0]
         ax.text(
             x,
             y + offset,
             f"Hub ({team_initial})",
-            fontsize=14,
+            fontsize=8,
             fontweight="bold",
             ha="center",
             va="bottom",
             color=INK,
             zorder=4,
-            bbox={"facecolor": ELEVATED_BG, "edgecolor": "none", "boxstyle": "round,pad=0.25", "alpha": 0.85},
+            bbox={"facecolor": ELEVATED_BG, "edgecolor": "none", "boxstyle": "round,pad=0.2", "alpha": 0.85},
         )
 
-# Title and frame
-ax.set_title("network-force-directed · matplotlib · anyplot.ai", fontsize=24, fontweight="medium", color=INK, pad=20)
+title = "network-force-directed · matplotlib · anyplot.ai"
+title_fontsize = max(8, round(12 * 67 / len(title))) if len(title) > 67 else 12
+ax.set_title(title, fontsize=title_fontsize, fontweight="medium", color=INK, pad=10)
 ax.set_xlim(-0.02, 1.02)
 ax.set_ylim(-0.02, 1.02)
 ax.axis("off")
 
-# Legend
 legend_handles = [
-    ax.scatter([], [], c=color, s=600, edgecolors=PAGE_BG, linewidths=2.0, label=name)
+    ax.scatter([], [], c=color, s=80, edgecolors=PAGE_BG, linewidths=1.2, label=name)
     for color, name in zip(COMMUNITY_COLORS, COMMUNITY_NAMES, strict=True)
 ]
 leg = ax.legend(
     handles=legend_handles,
     loc="upper left",
-    fontsize=16,
+    fontsize=8,
     title="Teams",
-    title_fontsize=18,
+    title_fontsize=10,
     framealpha=0.95,
     fancybox=True,
 )
@@ -163,16 +163,15 @@
 leg.get_title().set_color(INK)
 plt.setp(leg.get_texts(), color=INK_SOFT)
 
-# Footer
 fig.text(
     0.5,
-    0.02,
-    f"50 nodes · {len(edges)} edges · node size scales with degree",
+    0.01,
+    f"50 nodes · {len(all_edges)} edges · node size ∝ degree · dashed = cross-team bridges",
     ha="center",
     va="bottom",
-    fontsize=12,
+    fontsize=8,
     color=INK_MUTED,
 )
 
-plt.tight_layout()
-plt.savefig(f"plot-{THEME}.png", dpi=300, bbox_inches="tight", facecolor=PAGE_BG)
+fig.subplots_adjust(left=0.03, right=0.97, top=0.93, bottom=0.07)
+plt.savefig(OUTPUT_DIR / f"plot-{THEME}.png", dpi=400, facecolor=PAGE_BG)