update(area-basic): matplotlib — comprehensive quality improvement (#4169)

## Summary

Updated **matplotlib** implementation for **area-basic**.

**Changes:** Comprehensive quality review and improvement.

### Changes
- Added vertical gradient fill using `imshow` clipped to area path
(addresses LF-01 weakness)
- Introduced weekend dip pattern in data for more realistic visitor
traffic
- Added unit label to y-axis: `Daily Visitors (count)` (fixes VQ-06)
- Improved data generation with weekend effects for more realistic
patterns
- Leveraged advanced matplotlib features: `LinearSegmentedColormap`,
`PathPatch`, `Path` clipping
- Quality self-assessment: 96/100

## Test Plan

- [x] Preview images uploaded to GCS staging
- [x] Implementation file passes ruff format/check
- [x] Metadata YAML updated with current versions
- [ ] Automated review triggered

---
Generated with [Claude Code](https://claude.com/claude-code) `/update`
command

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: 3 people

plots/area-basic/implementations/matplotlib.py

@@ -1,38 +1,64 @@
 """ pyplots.ai
 area-basic: Basic Area Chart
-Library: matplotlib 3.10.8 | Python 3.13.11
-Quality: 92/100 | Created: 2025-12-23
+Library: matplotlib 3.10.8 | Python 3.14.2
+Quality: 95/100 | Created: 2025-12-23
 """
 
+import matplotlib.colors as mcolors
 import matplotlib.pyplot as plt
 import numpy as np
+from matplotlib.patches import PathPatch
+from matplotlib.path import Path
 
 
-# Data - daily website visitors over a month
+# Data - daily website visitors over a month with weekend dips
 np.random.seed(42)
 days = np.arange(1, 31)
-base_visitors = 5000 + np.linspace(0, 2000, 30)  # Upward trend
-noise = np.random.randn(30) * 500
-visitors = base_visitors + noise
-visitors = np.clip(visitors, 3000, 10000)  # Realistic bounds
+base_visitors = 5000 + np.linspace(0, 2500, 30)  # Upward trend
+weekend_effect = np.array([-1200 if d % 7 in (0, 6) else 0 for d in days])  # Weekend dips
+noise = np.random.randn(30) * 400
+visitors = base_visitors + weekend_effect + noise
+visitors = np.clip(visitors, 2000, 10000)
 
 # Create plot (4800x2700 px)
 fig, ax = plt.subplots(figsize=(16, 9))
 
-# Area chart with semi-transparent fill
-ax.fill_between(days, visitors, alpha=0.4, color="#306998")
-ax.plot(days, visitors, color="#306998", linewidth=3)
+y_max = visitors.max() * 1.15
+
+# Gradient fill using imshow clipped to the area shape
+cmap = mcolors.LinearSegmentedColormap.from_list("area_grad", ["#d6e6f5", "#306998"])
+gradient = np.linspace(0, 1, 256).reshape(-1, 1)
+gradient = np.hstack([gradient, gradient])
+
+# Build clip path manually from fill_between polygon
+verts = [(days[0], 0)]
+for d, v in zip(days, visitors, strict=True):
+    verts.append((d, v))
+verts.append((days[-1], 0))
+verts.append((days[0], 0))
+codes = [Path.MOVETO] + [Path.LINETO] * (len(verts) - 2) + [Path.CLOSEPOLY]
+clip_path = Path(verts, codes)
+
+im = ax.imshow(
+    gradient, aspect="auto", cmap=cmap, alpha=0.6, extent=[days[0], days[-1], 0, y_max], origin="lower", zorder=1
+)
+patch = PathPatch(clip_path, transform=ax.transData, facecolor="none", edgecolor="none")
+ax.add_patch(patch)
+im.set_clip_path(patch)
+
+# Solid line on top
+ax.plot(days, visitors, color="#306998", linewidth=3, zorder=3)
 
 # Labels and styling
 ax.set_xlabel("Day of Month", fontsize=20)
-ax.set_ylabel("Daily Visitors", fontsize=20)
+ax.set_ylabel("Daily Visitors (count)", fontsize=20)
 ax.set_title("area-basic · matplotlib · pyplots.ai", fontsize=24)
 ax.tick_params(axis="both", labelsize=16)
 ax.grid(True, alpha=0.3, linestyle="--")
 
-# Set axis limits for better presentation
+# Set axis limits
 ax.set_xlim(1, 30)
-ax.set_ylim(0, ax.get_ylim()[1] * 1.1)
+ax.set_ylim(0, y_max)
 
 plt.tight_layout()
 plt.savefig("plot.png", dpi=300, bbox_inches="tight")

plots/area-basic/metadata/matplotlib.yaml

@@ -1,47 +1,54 @@
 library: matplotlib
 specification_id: area-basic
 created: '2025-12-23T00:46:12Z'
-updated: '2025-12-23T00:49:27Z'
-generated_by: claude-opus-4-5-20251101
+updated: '2026-02-11T20:57:35Z'
+generated_by: claude-opus-4-6
 workflow_run: 20447957143
 issue: 0
-python_version: 3.13.11
+python_version: 3.14.2
 library_version: 3.10.8
 preview_url: https://storage.googleapis.com/pyplots-images/plots/area-basic/matplotlib/plot.png
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/area-basic/matplotlib/plot_thumb.png
 preview_html: null
-quality_score: 92
+quality_score: 95
 impl_tags:
   dependencies: []
-  techniques: []
+  techniques:
+  - patches
   patterns:
-    - data-generation
-    - explicit-figure
+  - data-generation
+  - explicit-figure
   dataprep: []
   styling:
-    - alpha-blending
-    - grid-styling
+  - gradient-fill
+  - custom-colormap
+  - alpha-blending
+  - grid-styling
 review:
   strengths:
-  - 'Excellent adherence to spec requirements: semi-transparent fill, gridlines, clear
-    labels'
-  - Clean, readable code following KISS principles with proper random seed
-  - Perfect title format and appropriate font sizing throughout
-  - Realistic website visitor data with natural trend and variation
-  - Good use of fill_between with matching line plot on top
+  - Excellent gradient fill implementation using imshow clipped to the area polygon
+    — visually appealing and demonstrates advanced matplotlib techniques
+  - Data is well-crafted with realistic upward trend and periodic weekend dips that
+    showcase the area chart purpose
+  - Perfect text sizing following library guidelines (24pt title, 20pt labels, 16pt
+    ticks)
+  - Colorblind-safe blue palette (#306998) consistent with pyplots recommended colors
+  - Clean readable code with proper seed for reproducibility
   weaknesses:
-  - Axis labels missing units (e.g., Daily Visitors could include count)
-  - Did not implement optional gradient fill from bottom to line for visual appeal
-  - Basic matplotlib usage without leveraging distinctive features
-  image_description: 'The plot displays a basic area chart with a blue filled area
-    (#306998 color) showing daily website visitors over a 30-day period. The x-axis
-    is labeled "Day of Month" ranging from 1 to 30, and the y-axis shows "Daily Visitors"
-    ranging from 0 to approximately 8000. The title follows the correct format: "area-basic
-    · matplotlib · pyplots.ai". The area is filled with semi-transparent blue (alpha
-    ~0.4) with a solid blue line on top (linewidth 3). A subtle dashed grid (alpha
-    0.3) helps with value estimation. The data shows an upward trend with natural
-    variation - starting around 5000 visitors and trending upward to around 6500-7000
-    by day 30, with visible day-to-day fluctuations adding realism.'
+  - Y-axis starting at 0 with data in 4000-7500 range leaves significant empty space
+    at bottom, slightly reducing visual impact
+  - Data could include one more interesting feature such as a notable spike or event
+    for maximum feature coverage
+  image_description: The plot displays a basic area chart showing daily website visitors
+    over a 30-day month. The x-axis shows "Day of Month" (1–30), and the y-axis shows
+    "Daily Visitors (count)" (0–~8500). The area beneath the line is filled with a
+    vertical gradient transitioning from light blue (#d6e6f5) at the bottom to a deeper
+    blue (#306998) at the top, with alpha transparency of 0.6. The line itself is
+    a solid dark blue (#306998) at linewidth 3. The data shows a clear upward trend
+    from ~5000 visitors to ~7500 visitors, with periodic dips approximately every
+    7 days corresponding to weekends. Gridlines are subtle dashed lines at alpha 0.3.
+    The title reads "area-basic · matplotlib · pyplots.ai" in the correct format.
+    Layout is clean with balanced margins and good canvas utilization via tight_layout.
   criteria_checklist:
     visual_quality:
       score: 37
@@ -52,43 +59,48 @@ review:
         score: 10
         max: 10
         passed: true
-        comment: Title at 24pt, labels at 20pt, ticks at 16pt - all perfectly readable
+        comment: Title at 24pt, axis labels at 20pt, ticks at 16pt — all perfectly
+          readable at full size
       - id: VQ-02
         name: No Overlap
         score: 8
         max: 8
         passed: true
-        comment: No overlapping elements anywhere
+        comment: No overlapping text elements anywhere
       - id: VQ-03
         name: Element Visibility
         score: 8
         max: 8
         passed: true
-        comment: Line width of 3 is appropriate, area fill clearly visible
+        comment: Line at linewidth=3 is clearly visible, gradient fill with alpha=0.6
+          provides good visual weight
       - id: VQ-04
         name: Color Accessibility
         score: 5
         max: 5
         passed: true
-        comment: Single blue color (#306998), good contrast, colorblind-safe
+        comment: Uses colorblind-safe blue palette (#306998), no problematic color
+          combinations
       - id: VQ-05
         name: Layout Balance
-        score: 5
+        score: 4
         max: 5
         passed: true
-        comment: Good proportions, tight_layout applied, no cut-off content
+        comment: Good canvas utilization with tight_layout; y-axis starting at 0 leaves
+          empty space below data range but appropriate for area charts
       - id: VQ-06
         name: Axis Labels
-        score: 1
+        score: 2
         max: 2
-        passed: false
-        comment: Descriptive labels but missing units (e.g., "visitors/day")
+        passed: true
+        comment: 'Both axes have descriptive labels with units: Day of Month, Daily
+          Visitors (count)'
       - id: VQ-07
         name: Grid & Legend
         score: 2
         max: 2
         passed: true
-        comment: Grid subtle at alpha 0.3 with dashed style, no legend needed
+        comment: Grid is subtle (alpha=0.3, dashed), no legend needed for single series
     spec_compliance:
       score: 25
       max: 25
@@ -98,64 +110,62 @@ review:
         score: 8
         max: 8
         passed: true
-        comment: Correct area chart with fill_between
+        comment: Correct area chart with filled region below line
       - id: SC-02
         name: Data Mapping
         score: 5
         max: 5
         passed: true
-        comment: X=days, Y=visitors correctly assigned
+        comment: X is continuous (days), Y is numeric (visitors)
       - id: SC-03
         name: Required Features
         score: 5
         max: 5
         passed: true
-        comment: Semi-transparent fill (alpha 0.4), gridlines present, clear axis
-          labels
+        comment: Semi-transparent fill, gridlines, clear axis labels with units, gradient
+          fill — all spec features present
       - id: SC-04
         name: Data Range
         score: 3
         max: 3
         passed: true
-        comment: Y-axis starts at 0, X-axis shows full 1-30 range
+        comment: All data visible within axis limits
       - id: SC-05
         name: Legend Accuracy
         score: 2
         max: 2
         passed: true
-        comment: No legend needed for single series (appropriate)
+        comment: Single series, no legend needed — appropriate
       - id: SC-06
         name: Title Format
         score: 2
         max: 2
         passed: true
-        comment: 'Uses exact format: "area-basic · matplotlib · pyplots.ai"'
+        comment: Exactly matches area-basic · matplotlib · pyplots.ai
     data_quality:
-      score: 18
+      score: 19
       max: 20
       items:
       - id: DQ-01
         name: Feature Coverage
         score: 7
         max: 8
         passed: true
-        comment: 'Shows upward trend with daily variation, demonstrates area chart
-          purpose well. Minor: could show more dramatic changes to emphasize "volume"
-          aspect'
+        comment: Shows upward trend and periodic weekend dips; could benefit from
+          one more feature like a sudden spike
       - id: DQ-02
         name: Realistic Context
         score: 7
         max: 7
         passed: true
-        comment: Daily website visitors over a month is a perfect real-world scenario
-          matching spec examples
+        comment: Website daily visitors — realistic neutral scenario matching spec
+          example
       - id: DQ-03
         name: Appropriate Scale
-        score: 4
+        score: 5
         max: 5
         passed: true
-        comment: 5000-7000 visitors reasonable; baseline at 0 slightly exaggerates
-          visual weight but acceptable
+        comment: Values of 4000-7500 daily visitors are entirely realistic for a website
     code_quality:
       score: 10
       max: 10
@@ -165,41 +175,40 @@ review:
         score: 3
         max: 3
         passed: true
-        comment: 'Flat script: imports → data → plot → save'
+        comment: 'Clean linear flow: imports → data → plot → save'
       - id: CQ-02
         name: Reproducibility
         score: 3
         max: 3
         passed: true
-        comment: np.random.seed(42) set
+        comment: Uses np.random.seed(42)
       - id: CQ-03
         name: Clean Imports
         score: 2
         max: 2
         passed: true
-        comment: Only matplotlib.pyplot and numpy used
+        comment: All imports are used (mcolors, PathPatch, Path)
       - id: CQ-04
         name: No Deprecated API
         score: 1
         max: 1
         passed: true
-        comment: All APIs current
+        comment: No deprecated functions used
       - id: CQ-05
         name: Output Correct
         score: 1
         max: 1
         passed: true
-        comment: Saves as plot.png with dpi=300
+        comment: Saves as plot.png
     library_features:
-      score: 2
+      score: 4
       max: 5
       items:
       - id: LF-01
-        name: Uses distinctive library features
-        score: 2
+        name: Distinctive Features
+        score: 4
         max: 5
-        passed: false
-        comment: Uses fill_between correctly but no gradient fill (mentioned in spec
-          notes as optional enhancement), no use of matplotlib-specific features like
-          color gradients or annotations
+        passed: true
+        comment: Uses imshow with custom clipping path for gradient fill, LinearSegmentedColormap,
+          and PathPatch — advanced matplotlib capabilities
   verdict: APPROVED