feat(matplotlib): implement heatmap-basic (#1380)

## Implementation: `heatmap-basic` - matplotlib

Implements the **matplotlib** version of `heatmap-basic`.

**File:** `plots/heatmap-basic/implementations/matplotlib.py`

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20447951294)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/heatmap-basic/implementations/matplotlib.py

@@ -1,7 +1,7 @@
 """ pyplots.ai
 heatmap-basic: Basic Heatmap
 Library: matplotlib 3.10.8 | Python 3.13.11
-Quality: 95/100 | Created: 2025-12-14
+Quality: 94/100 | Created: 2025-12-23
 """
 
 import matplotlib.pyplot as plt
@@ -19,16 +19,16 @@
 np.fill_diagonal(data, 1)  # Perfect correlation on diagonal
 data = np.clip(data, -1, 1)  # Clip to valid correlation range
 
-# Create plot (4800x2700 px)
-fig, ax = plt.subplots(figsize=(16, 9))
+# Create plot (3600x3600 px - square format best for heatmaps)
+fig, ax = plt.subplots(figsize=(12, 12))
 
 # Heatmap with diverging colormap for positive/negative values
-im = ax.imshow(data, cmap="RdBu_r", vmin=-1, vmax=1, aspect="auto")
+im = ax.imshow(data, cmap="RdBu_r", vmin=-1, vmax=1, aspect="equal")
 
 # Add colorbar
 cbar = fig.colorbar(im, ax=ax, shrink=0.8, pad=0.02)
 cbar.ax.tick_params(labelsize=16)
-cbar.set_label("Correlation", fontsize=18)
+cbar.set_label("Correlation Coefficient", fontsize=18)
 
 # Set ticks and labels
 ax.set_xticks(np.arange(n))
@@ -42,12 +42,12 @@
         value = data[i, j]
         # Use white text on dark cells, black on light cells
         text_color = "white" if abs(value) > 0.5 else "black"
-        ax.text(j, i, f"{value:.2f}", ha="center", va="center", fontsize=14, color=text_color)
+        ax.text(j, i, f"{value:.2f}", ha="center", va="center", fontsize=14, color=text_color, fontweight="bold")
 
 # Labels and title
 ax.set_xlabel("Department", fontsize=20)
 ax.set_ylabel("Department", fontsize=20)
-ax.set_title("heatmap-basic · matplotlib · pyplots.ai", fontsize=24)
+ax.set_title("heatmap-basic · matplotlib · pyplots.ai", fontsize=24, pad=15)
 
 plt.tight_layout()
 plt.savefig("plot.png", dpi=300, bbox_inches="tight")

plots/heatmap-basic/metadata/matplotlib.yaml

@@ -1,17 +1,28 @@
 library: matplotlib
 specification_id: heatmap-basic
-created: 2025-12-14 09:13:34+00:00
-updated: 2025-12-14 09:13:34+00:00
+created: '2025-12-23T00:46:03Z'
+updated: '2025-12-23T00:49:08Z'
 generated_by: claude-opus-4-5-20251101
-workflow_run: 20205723953
-issue: 691
+workflow_run: 20447951294
+issue: 0
 python_version: 3.13.11
 library_version: 3.10.8
 preview_url: https://storage.googleapis.com/pyplots-images/plots/heatmap-basic/matplotlib/plot.png
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/heatmap-basic/matplotlib/plot_thumb.png
 preview_html: null
-quality_score: 95
+quality_score: 94
 review:
-  strengths: []
-  weaknesses: []
-  improvements: []
+  strengths:
+  - Excellent use of adaptive text colors (white on dark, black on light) for cell
+    annotations ensuring readability
+  - 'Perfect implementation of spec requirements: diverging colormap (RdBu_r), cell
+    annotations, and colorbar'
+  - Clean, symmetric correlation matrix with realistic department names providing
+    meaningful context
+  - Square aspect ratio (12×12) ideal for matrix visualization
+  - Well-sized fonts throughout (24pt title, 20pt labels, 16pt ticks, 14pt annotations)
+  weaknesses:
+  - Could use matplotlib-specific features like ax.matshow() instead of ax.imshow()
+    for more idiomatic matrix display
+  - Department axis labels could include additional context (e.g., "Department" →
+    "Department Correlation")