feat(plotnine): implement line-stress-strain

plots/line-stress-strain/implementations/plotnine.py

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+""" pyplots.ai
+line-stress-strain: Engineering Stress-Strain Curve
+Library: plotnine 0.15.3 | Python 3.14.3
+Quality: 90/100 | Created: 2026-03-20
+"""
+
+import numpy as np
+import pandas as pd
+from plotnine import (
+    aes,
+    annotate,
+    coord_cartesian,
+    element_blank,
+    element_line,
+    element_rect,
+    element_text,
+    geom_line,
+    geom_point,
+    geom_segment,
+    geom_text,
+    ggplot,
+    labs,
+    scale_color_identity,
+    scale_fill_identity,
+    scale_linetype_identity,
+    scale_size_identity,
+    scale_x_continuous,
+    scale_y_continuous,
+    theme,
+    theme_minimal,
+)
+
+
+# Data - Mild steel stress-strain curve
+np.random.seed(42)
+
+youngs_modulus = 210000  # MPa
+yield_stress = 250  # MPa
+uts = 400  # MPa
+fracture_strain = 0.35
+necking_strain = 0.22
+
+# Elastic region (0 to yield)
+elastic_strain = np.linspace(0, yield_stress / youngs_modulus, 40)
+elastic_stress = youngs_modulus * elastic_strain
+
+# Yield plateau (short flat region for mild steel)
+plateau_strain = np.linspace(elastic_strain[-1], 0.025, 15)
+plateau_stress = np.full_like(plateau_strain, yield_stress)
+
+# Strain hardening (power law)
+hardening_strain = np.linspace(0.025, necking_strain, 80)
+hardening_stress = yield_stress + (uts - yield_stress) * ((hardening_strain - 0.025) / (necking_strain - 0.025)) ** 0.45
+
+# Necking to fracture (stress decreases)
+necking_strain_vals = np.linspace(necking_strain, fracture_strain, 40)
+necking_stress = (
+    uts - (uts - 320) * ((necking_strain_vals - necking_strain) / (fracture_strain - necking_strain)) ** 1.3
+)
+
+# Combine all regions
+strain = np.concatenate([elastic_strain, plateau_strain[1:], hardening_strain[1:], necking_strain_vals[1:]])
+stress = np.concatenate([elastic_stress, plateau_stress[1:], hardening_stress[1:], necking_stress[1:]])
+
+df = pd.DataFrame({"strain": strain, "stress": stress})
+
+# 0.2% offset line data - extended for better visibility
+offset = 0.002
+offset_strain_start = offset
+offset_strain_end = (yield_stress + 50) / youngs_modulus + offset
+
+# Key points
+yield_point_strain = yield_stress / youngs_modulus + offset
+yield_point_stress = yield_stress
+uts_strain = necking_strain
+uts_stress = uts
+fracture_strain_pt = fracture_strain
+fracture_stress_pt = necking_stress[-1]
+
+df_points = pd.DataFrame(
+    {
+        "strain": [yield_point_strain, uts_strain, fracture_strain_pt],
+        "stress": [yield_point_stress, uts_stress, fracture_stress_pt],
+        "label": ["Yield Point\n(0.2% offset)", "UTS", "Fracture"],
+        "color": ["#C0392B", "#C0392B", "#C0392B"],
+        "size": [6.0, 6.0, 6.0],
+    }
+)
+
+# Region labels - repositioned for clarity
+df_regions = pd.DataFrame(
+    {
+        "strain": [0.005, 0.015, 0.13, 0.29],
+        "stress": [410, 215, 310, 370],
+        "label": ["Elastic", "Yield\nPlateau", "Strain\nHardening", "Necking"],
+        "color": ["#5D6D7E", "#5D6D7E", "#5D6D7E", "#5D6D7E"],
+    }
+)
+
+# Region boundary strains for shading
+elastic_end = yield_stress / youngs_modulus
+plateau_end = 0.025
+
+# Plot using plotnine grammar of graphics with layered composition
+plot = (
+    ggplot()
+    # Region shading using annotate("rect") - plotnine-distinctive feature
+    + annotate("rect", xmin=0, xmax=elastic_end, ymin=0, ymax=440, alpha=0.15, fill="#3498DB")
+    + annotate("rect", xmin=elastic_end, xmax=plateau_end, ymin=0, ymax=440, alpha=0.15, fill="#2ECC71")
+    + annotate("rect", xmin=plateau_end, xmax=necking_strain, ymin=0, ymax=440, alpha=0.12, fill="#F39C12")
+    + annotate("rect", xmin=necking_strain, xmax=fracture_strain, ymin=0, ymax=440, alpha=0.12, fill="#E74C3C")
+    # Main stress-strain curve
+    + geom_line(df, aes(x="strain", y="stress"), color="#306998", size=2.8)
+    # 0.2% offset line using geom_segment - plotnine-distinctive
+    + geom_segment(
+        aes(x=offset_strain_start, xend=offset_strain_end, y=0, yend=yield_stress + 50),
+        color="#C0392B",
+        size=1.2,
+        linetype="dashed",
+    )
+    # Offset label near the line
+    + annotate("text", x=0.012, y=60, label="0.2% offset", size=11, color="#C0392B", fontstyle="italic")
+    # Key points with identity scales for direct aesthetic mapping
+    + geom_point(df_points, aes(x="strain", y="stress", color="color", size="size"), fill="#C0392B")
+    + scale_color_identity()
+    + scale_size_identity()
+    # Point labels - larger text
+    + geom_text(
+        df_points, aes(x="strain", y="stress", label="label"), nudge_y=32, size=15, color="#2C3E50", fontweight="bold"
+    )
+    # Region labels with identity color scale - larger text
+    + geom_text(df_regions, aes(x="strain", y="stress", label="label", color="color"), size=14, fontstyle="italic")
+    + scale_fill_identity()
+    + scale_linetype_identity()
+    # Modulus annotation - larger and repositioned
+    + annotate(
+        "text", x=0.03, y=140, label=f"E = {youngs_modulus // 1000} GPa", size=16, color="#306998", fontweight="bold"
+    )
+    + labs(x="Engineering Strain", y="Engineering Stress (MPa)", title="line-stress-strain · plotnine · pyplots.ai")
+    + scale_x_continuous(breaks=np.arange(0, 0.40, 0.05))
+    + scale_y_continuous(breaks=np.arange(0, 500, 50))
+    # Coordinate control - plotnine-distinctive
+    + coord_cartesian(xlim=(0, 0.38), ylim=(0, 460))
+    + theme_minimal()
+    + theme(
+        figure_size=(16, 9),
+        plot_title=element_text(size=26, weight="bold", color="#1A2530"),
+        axis_title=element_text(size=22, color="#2C3E50", weight="bold"),
+        axis_text=element_text(size=16, color="#555555"),
+        panel_grid_major_x=element_blank(),
+        panel_grid_minor=element_blank(),
+        panel_grid_major_y=element_line(color="#E8E8E8", size=0.4, alpha=0.5),
+        plot_background=element_rect(fill="white", color="white"),
+        panel_background=element_rect(fill="white", color="white"),
+    )
+)
+
+# Save
+plot.save("plot.png", dpi=300, verbose=False)

plots/line-stress-strain/metadata/plotnine.yaml

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+library: plotnine
+specification_id: line-stress-strain
+created: '2026-03-20T21:22:28Z'
+updated: '2026-03-20T21:43:25Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 23363004971
+issue: 4413
+python_version: 3.14.3
+library_version: 0.15.3
+preview_url: https://storage.googleapis.com/pyplots-images/plots/line-stress-strain/plotnine/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/line-stress-strain/plotnine/plot_thumb.png
+preview_html: null
+quality_score: 90
+review:
+  strengths:
+  - Excellent data storytelling through color-coded region shading that guides the
+    viewer through material behavior phases
+  - 'All spec-required features implemented: region labels, critical points, elastic
+    modulus annotation, 0.2% offset line'
+  - Realistic mild steel data with appropriate engineering values
+  - Clean, well-structured code following KISS principles
+  - Good use of plotnine grammar-of-graphics approach with layered composition
+  weaknesses:
+  - The elastic region is horizontally compressed, creating visual density with multiple
+    labels in a narrow space
+  - The 0.2% offset annotation text (size=11) is noticeably smaller than other text
+    elements
+  image_description: 'The plot displays an engineering stress-strain curve for mild
+    steel on a white background. The title "line-stress-strain · plotnine · pyplots.ai"
+    appears in bold dark text at the top. The x-axis is labeled "Engineering Strain"
+    (0.00–0.35) and the y-axis "Engineering Stress (MPa)" (0–450). A thick dark blue
+    line traces the characteristic stress-strain path from origin through elastic
+    deformation, yield plateau, strain hardening up to ~400 MPa at strain ~0.22 (UTS),
+    then necking down to ~320 MPa at fracture (strain ~0.35). Four color-shaded rectangular
+    regions mark the material behavior zones: light blue (Elastic), light green (Yield
+    Plateau), light yellow/orange (Strain Hardening), and light pink/red (Necking),
+    each with gray italic region labels. Three red dots mark critical points labeled
+    in bold: "Yield Point (0.2% offset)", "UTS", and "Fracture". A red dashed line
+    shows the 0.2% offset construction with a small red italic "0.2% offset" label
+    near the bottom. "E = 210 GPa" appears in bold blue text. The y-axis grid is subtle
+    light gray; x-axis grid is removed. Layout is 16:9 with good canvas utilization.'
+  criteria_checklist:
+    visual_quality:
+      score: 28
+      max: 30
+      items:
+      - id: VQ-01
+        name: Text Legibility
+        score: 7
+        max: 8
+        passed: true
+        comment: All major text sizes explicitly set (title=26, axis_title=22, axis_text=16).
+          The 0.2% offset annotation at size=11 is smaller than other text.
+      - id: VQ-02
+        name: No Overlap
+        score: 5
+        max: 6
+        passed: true
+        comment: No actual text overlap, but elastic region is horizontally compressed
+          with multiple labels in a narrow band.
+      - id: VQ-03
+        name: Element Visibility
+        score: 6
+        max: 6
+        passed: true
+        comment: Main curve at size=2.8 clearly visible, key points at size=6 are
+          prominent.
+      - id: VQ-04
+        name: Color Accessibility
+        score: 4
+        max: 4
+        passed: true
+        comment: Blue curve with red accents, pastel region shading. Colorblind-safe,
+          no red-green dependency.
+      - id: VQ-05
+        name: Layout & Canvas
+        score: 4
+        max: 4
+        passed: true
+        comment: Good 16:9 proportions with plot filling the canvas well.
+      - id: VQ-06
+        name: Axis Labels & Title
+        score: 2
+        max: 2
+        passed: true
+        comment: 'Descriptive labels with units: Engineering Strain and Engineering
+          Stress (MPa).'
+    design_excellence:
+      score: 15
+      max: 20
+      items:
+      - id: DE-01
+        name: Aesthetic Sophistication
+        score: 6
+        max: 8
+        passed: true
+        comment: Color-coded region shading, custom palette, intentional typographic
+          hierarchy. Above defaults.
+      - id: DE-02
+        name: Visual Refinement
+        score: 4
+        max: 6
+        passed: true
+        comment: X-grid removed, subtle y-only grid, clean white background. Minor
+          density in elastic region.
+      - id: DE-03
+        name: Data Storytelling
+        score: 5
+        max: 6
+        passed: true
+        comment: Color-coded regions guide viewer through material behavior. Key points
+          create clear focal points.
+    spec_compliance:
+      score: 15
+      max: 15
+      items:
+      - id: SC-01
+        name: Plot Type
+        score: 5
+        max: 5
+        passed: true
+        comment: Correct engineering stress-strain curve as line plot.
+      - id: SC-02
+        name: Required Features
+        score: 4
+        max: 4
+        passed: true
+        comment: 'All spec features present: region labels, critical points, modulus
+          annotation, offset line.'
+      - id: SC-03
+        name: Data Mapping
+        score: 3
+        max: 3
+        passed: true
+        comment: X=strain, Y=stress correctly mapped with full data range.
+      - id: SC-04
+        name: Title & Legend
+        score: 3
+        max: 3
+        passed: true
+        comment: Title follows exact format. No legend needed for single-series.
+    data_quality:
+      score: 15
+      max: 15
+      items:
+      - id: DQ-01
+        name: Feature Coverage
+        score: 6
+        max: 6
+        passed: true
+        comment: 'Shows all curve regions: elastic, yield plateau, strain hardening,
+          necking, fracture.'
+      - id: DQ-02
+        name: Realistic Context
+        score: 5
+        max: 5
+        passed: true
+        comment: Mild steel tensile test - classic, neutral engineering scenario.
+      - id: DQ-03
+        name: Appropriate Scale
+        score: 4
+        max: 4
+        passed: true
+        comment: 'Realistic values for mild steel: E=210 GPa, yield=250 MPa, UTS=400
+          MPa.'
+    code_quality:
+      score: 10
+      max: 10
+      items:
+      - id: CQ-01
+        name: KISS Structure
+        score: 3
+        max: 3
+        passed: true
+        comment: 'Clean linear flow: imports, data, plot, save. No functions or classes.'
+      - id: CQ-02
+        name: Reproducibility
+        score: 2
+        max: 2
+        passed: true
+        comment: np.random.seed(42) set at start.
+      - id: CQ-03
+        name: Clean Imports
+        score: 2
+        max: 2
+        passed: true
+        comment: All imports are used.
+      - id: CQ-04
+        name: Code Elegance
+        score: 2
+        max: 2
+        passed: true
+        comment: Well-organized with clear sections. No fake UI.
+      - id: CQ-05
+        name: Output & API
+        score: 1
+        max: 1
+        passed: true
+        comment: Saves as plot.png with dpi=300. Current plotnine API.
+    library_mastery:
+      score: 7
+      max: 10
+      items:
+      - id: LM-01
+        name: Idiomatic Usage
+        score: 4
+        max: 5
+        passed: true
+        comment: Good grammar-of-graphics with layered composition, aes mapping, identity
+          scales, theme customization.
+      - id: LM-02
+        name: Distinctive Features
+        score: 3
+        max: 5
+        passed: true
+        comment: Uses annotate rect for region shading, coord_cartesian, identity
+          scales, geom_segment.
+  verdict: APPROVED
+impl_tags:
+  dependencies: []
+  techniques:
+  - annotations
+  - layer-composition
+  patterns:
+  - data-generation
+  dataprep: []
+  styling:
+  - alpha-blending
+  - grid-styling