feat(pygal): implement line-stress-strain

[github-actions]

Implementation: line-stress-strain - python/pygal

Implements the python/pygal version of line-stress-strain.

File: plots/line-stress-strain/implementations/python/pygal.py

Parent Issue: #4413

---

🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

Light render (plot-light.png): Warm off-white background (#FAF8F1). Title "line-stress-strain · python · pygal · anyplot.ai" rendered in dark ink spanning ~65% of canvas width — appropriate for the mandated title length. Y-axis label "Engineering Stress (MPa)" rotated vertically, readable. X-axis label "Engineering Strain (dimensionless)" clearly readable. Tick labels (0–0.26 on X; 0–400 on Y) all legible in dark ink. Two data curves: green (#009E73) ASTM A36 Mild Steel showing elastic rise, Lüders plateau, strain hardening to UTS ~450 MPa at strain ~0.21, then necking to fracture at ~0.27; lavender (#C475FD) 6061-T6 Aluminum with smooth hardening to UTS ~310 MPa at strain ~0.095 then necking/fracture at ~0.12. Thin dashed blue (#4467A3) 0.2% offset line visible but very thin near x=0.002–0.007. Legend at bottom with three entries, readable. No visible region labels (elastic/plastic/necking), no critical point markers, no elastic modulus annotation appear in the static PNG. All text readable against light background. Legibility: PASS.

Dark render (plot-dark.png): Background is warm near-black (#1A1A17). Title, axis labels, tick labels, and legend all render in light-colored text clearly readable against the dark surface — no dark-on-dark failures observed. Data colors are identical to the light render: green (#009E73) steel curve, lavender (#C475FD) aluminum curve, thin dashed blue (#4467A3) offset line. Both curves clearly distinguishable against the dark background. Brand green #009E73 remains clearly visible. Same absence of annotations as light render. Legibility: PASS.

Both paragraphs confirmed. Data colors identical across themes. Chrome correctly flips between renders.

Score: 79/100

Category	Score	Max
Visual Quality	26	30
Design Excellence	9	20
Spec Compliance	12	15
Data Quality	15	15
Code Quality	10	10
Library Mastery	7	10
Total	79	100

Visual Quality (26/30)

• VQ-01: Text Legibility (7/8) — All font sizes explicitly set in Style object. Title, axis labels, ticks readable in both themes. Proportions balanced.
• VQ-02: No Overlap (6/6) — No text overlap. Legend at bottom clean.
• VQ-03: Element Visibility (4/6) — Main curves well visible. The 0.2% offset line is very thin (stroke width=2 vs data series 3.5) and barely distinguishable in both renders. Critical point markers absent from PNG (tooltip-only).
• VQ-04: Color Accessibility (2/2) — Green/purple/blue combination CVD-safe and distinguishable.
• VQ-05: Layout & Canvas (3/4) — Chart fills canvas well. Steel data extends to x=0.27; aluminum fractures at x=0.12, leaving lower-right sparse — this is data-driven and acceptable.
• VQ-06: Axis Labels & Title (2/2) — Both axes descriptive with units.
• VQ-07: Palette Compliance (2/2) — Imprint palette canonical order (#009E73, #C475FD, #4467A3). Backgrounds correct. Data colors identical across themes.

Design Excellence (9/20)

• DE-01: Aesthetic Sophistication (4/8) — Well-configured library default: correct Imprint palette, theme-adaptive tokens, clean typography. No visual hierarchy beyond color; no emphasis or focal points.
• DE-02: Visual Refinement (3/6) — Y-axis-only grid is a good choice. Legend at bottom is clean. All spines present (pygal constraint). No additional refinement beyond the Style object.
• DE-03: Data Storytelling (2/6) — Two-material comparison frames a story, but the key storytelling elements required by the spec (region labels, critical point markers, elastic modulus annotation) are absent from the static PNG.

Spec Compliance (12/15)

• SC-01: Plot Type (5/5) — Correct: XY line chart for stress-strain.
• SC-02: Required Features (1/4) — Spec requires four annotation features; only one is present: (1) region labels (elastic/plastic/necking) — absent in PNG; (2) critical point markers (yield, UTS, fracture) — tooltip-only, not visible in PNG; (3) elastic modulus slope line or text annotation — entirely absent; (4) 0.2% offset line — present (but thin). Multi-material overlay done.
• SC-03: Data Mapping (3/3) — Strain on X, stress (MPa) on Y, both materials fully displayed.
• SC-04: Title & Legend (3/3) — Title format correct. Legend labels descriptive.

Data Quality (15/15)

• DQ-01: Feature Coverage (6/6) — Covers all regions: elastic, Lüders plateau (mild steel only), strain hardening, necking, fracture. Two materials show contrasting behaviors.
• DQ-02: Realistic Context (5/5) — Real engineering materials with real designations (ASTM A36, 6061-T6). Neutral scientific context.
• DQ-03: Appropriate Scale (4/4) — ASTM A36: E=200 GPa, yield=250 MPa, UTS~450 MPa (correct). 6061-T6: E=68.5 GPa, yield=276 MPa, UTS=310 MPa (correct). Noise levels realistic.

Code Quality (10/10)

• CQ-01: KISS Structure (3/3) — Clean linear structure, no functions/classes.
• CQ-02: Reproducibility (2/2) — np.random.seed(42) set.
• CQ-03: Clean Imports (2/2) — All imports used.
• CQ-04: Code Elegance (2/2) — Clean, Pythonic. Per-point dict format for tooltip labels is appropriate.
• CQ-05: Output & API (1/1) — Saves plot-{THEME}.png and plot-{THEME}.html correctly.

Library Mastery (7/10)

• LM-01: Idiomatic Usage (4/5) — Good use of pygal.XY for continuous coordinates. Style object, stroke_style with dasharray, and HTML export all correct.
• LM-02: Distinctive Features (3/5) — Per-point label dict format for tooltips is pygal-distinctive. HTML export with interactive SVG tooltips leverages pygal's interactive nature.

Score Caps Applied

• None — DE-01=4 and DE-02=3, no "correct but boring" cap (requires both ≤2). No other caps triggered.

Strengths

• Physically accurate dual-material dataset with correct ASTM A36 and 6061-T6 aluminum parameters (E, yield, UTS)
• Covers all stress-strain regions: elastic, Lüders plateau, strain hardening, necking, fracture
• Perfect code quality: KISS structure, reproducible, clean imports, correct PNG + HTML output
• Correct Imprint palette in canonical order; theme-adaptive chrome; both renders fully readable

Weaknesses

• Missing visible region labels in PNG: spec requires labeling elastic, plastic/strain hardening, and necking regions directly on the chart — tooltip labels do not appear in static output
• Missing critical point markers in PNG: yield point, UTS, and fracture point are only in pygal tooltips (HTML-only); the static PNG shows no markers or annotations at these points
• Missing elastic modulus annotation: spec explicitly requires annotating Young's modulus with a visible slope line or text annotation in the elastic region — entirely absent
• 0.2% offset line too thin: stroke width=2 vs data series width=3.5 makes it barely visible, especially in dark render — increase to width=4–5 or use a more prominent style
• No visual refinement: all spines present, no emphasis elements — chart reads as functional rather than polished

Issues Found

1. SC-02 LOW (1/4): Three of four required spec annotation features missing from static PNG
   • Fix: Add pygal-compatible visual annotations — since pygal doesn't support arbitrary text overlays natively, consider: (a) adding a separate legend-style series for region boundaries using horizontal/vertical reference lines rendered via extra XY data points, or (b) using pygal's / mechanism for reference markers, or (c) adding a fourth series as a thin vertical line at the yield strain with a label entry in the legend noting "Yield Point"
   • At minimum: add the elastic modulus slope as an additional XY line series labeled "E = 200 GPa (slope)" in the legend; add markers as separate single-point series for yield/UTS/fracture with descriptive legend labels so they appear in the static PNG
2. VQ-03 MINOR: 0.2% offset line nearly invisible
   • Fix: Increase stroke_style width from 2 to 4–5; consider using a more prominent dash pattern (e.g. dasharray="12, 6")
3. DE-01/DE-02 LOW: Generic design without visual refinement
   • Fix: Use color emphasis (e.g., make the mild steel curve slightly thicker as the primary specimen), consider adding a fill="below" or region shading for the elastic zone if feasible in pygal

AI Feedback for Next Attempt

The implementation has excellent data quality and code quality but is missing the core spec requirements for static annotations. Since pygal doesn't support arbitrary positioned text overlays like matplotlib, use workarounds: (1) add the elastic modulus slope as a named XY series (e.g., 3 points along the slope labeled "E ≈ 200 GPa" in legend); (2) add yield/UTS/fracture as separate single-point series with show_dots=True and descriptive legend labels so they appear as markers in the PNG; (3) add region boundary reference lines as thin vertical XY series (e.g., at x=yield_strain labeled "Yield" in legend). Also increase the 0.2% offset line stroke width to 4–5 for better visibility.

Verdict: REJECTED

[github-actions]

🔧 Repair Workflow Crashed (Attempt 1/4) — Auto-Retrying

The repair workflow failed (probably a transient Claude Code Action issue). Automatically re-triggering this attempt...

---

🤖 impl-repair

[github-actions]

❌ Repair Workflow Crashed (Attempt 1/4, retry exhausted)

The repair workflow itself failed twice for this attempt — likely a persistent Claude Code Action issue.

Manual restart:

gh workflow run impl-repair.yml -f pr_number=9299 -f specification_id=line-stress-strain -f library=pygal -f attempt=1 -f model=sonnet

---

🤖 impl-repair