feat(plotnine): implement stem-basic

plots/stem-basic/implementations/python/plotnine.py

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+""" anyplot.ai
+stem-basic: Basic Stem Plot
+Library: plotnine 0.15.3 | Python 3.13.13
+Quality: 87/100 | Created: 2026-04-30
+"""
+
+import os
+
+import numpy as np
+import pandas as pd
+from plotnine import (
+    aes,
+    element_line,
+    element_rect,
+    element_text,
+    geom_hline,
+    geom_point,
+    geom_segment,
+    ggplot,
+    labs,
+    theme,
+    theme_minimal,
+)
+
+
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+
+BRAND = "#009E73"
+
+# Data - Damped sinusoidal discrete signal (signal processing example)
+np.random.seed(42)
+n = 30
+t = np.arange(n)
+signal = np.exp(-t / 12.0) * np.cos(0.55 * t)
+
+df = pd.DataFrame({"t": t, "signal": signal, "zero": 0.0})
+
+# Plot
+plot = (
+    ggplot(df, aes(x="t"))
+    + geom_hline(yintercept=0, color=INK_SOFT, size=0.8)
+    + geom_segment(aes(x="t", xend="t", y="zero", yend="signal"), color=BRAND, size=0.9)
+    + geom_point(aes(y="signal"), color=BRAND, size=4, stroke=0.5)
+    + labs(x="Sample Index", y="Amplitude", title="stem-basic · plotnine · anyplot.ai")
+    + theme_minimal()
+    + theme(
+        figure_size=(16, 9),
+        plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
+        panel_background=element_rect(fill=PAGE_BG),
+        text=element_text(size=14, color=INK),
+        axis_title=element_text(size=20, color=INK),
+        axis_text=element_text(size=16, color=INK_SOFT),
+        plot_title=element_text(size=24, color=INK),
+        panel_grid_major_y=element_line(color=INK, size=0.3, alpha=0.10),
+        panel_grid_major_x=element_line(color=INK, size=0.0, alpha=0.0),
+        panel_grid_minor=element_line(color=INK, size=0.2, alpha=0.05),
+        axis_line=element_line(color=INK_SOFT),
+    )
+)
+
+# Save
+plot.save(f"plot-{THEME}.png", dpi=300, width=16, height=9, verbose=False)

plots/stem-basic/metadata/python/plotnine.yaml

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+library: plotnine
+language: python
+specification_id: stem-basic
+created: '2026-04-30T15:18:15Z'
+updated: '2026-04-30T15:34:36Z'
+generated_by: claude-sonnet
+workflow_run: 25172265081
+issue: 972
+python_version: 3.13.13
+library_version: 0.15.3
+preview_url_light: https://storage.googleapis.com/anyplot-images/plots/stem-basic/python/plotnine/plot-light.png
+preview_url_dark: https://storage.googleapis.com/anyplot-images/plots/stem-basic/python/plotnine/plot-dark.png
+preview_html_light: null
+preview_html_dark: null
+quality_score: 87
+review:
+  strengths:
+  - 'Perfect spec compliance: all stem plot features (stems, markers, baseline) implemented
+    correctly using plotnine''s grammar of graphics (geom_segment + geom_point + geom_hline)'
+  - 'Excellent theme adaptation: both light and dark renders are fully legible with
+    correct backgrounds (#FAF8F1 / #1A1A17), text colors, and adaptive grid tokens'
+  - 'Compelling realistic data: damped sinusoidal signal is a natural fit for a stem
+    plot and demonstrates positive/negative values, oscillation, and amplitude decay'
+  - 'Refined grid design: y-axis-only grid at 10% opacity with x-axis grid suppressed
+    — an intentional and excellent visual choice'
+  weaknesses:
+  - Y-axis label 'Amplitude' lacks units/context — 'Amplitude (normalized)' would
+    be more informative and score full points on VQ-06
+  - No visual storytelling or hierarchy — the decay pattern in the damped sinusoidal
+    signal is not visually emphasized through size variation, alpha, or a reference
+    envelope curve, leaving DE-03 at default level
+  image_description: |-
+    Light render (plot-light.png):
+      Background: Warm off-white #FAF8F1 — correct, not pure white
+      Chrome: Title "stem-basic · plotnine · anyplot.ai" in dark #1A1A17, clearly readable. X-axis label "Sample Index" and y-axis label "Amplitude" in dark ink. Tick labels in muted #4A4A44. All text readable against light background.
+      Data: 30 stems in brand green #009E73 — thin vertical lines from y=0 baseline to filled circle markers. Baseline at y=0 as a darker horizontal reference line. Y-axis-only subtle grid at ~10% opacity. No legend (single series).
+      Legibility verdict: PASS
+
+    Dark render (plot-dark.png):
+      Background: Near-black #1A1A17 — correct, not pure black
+      Chrome: Title in light #F0EFE8, clearly readable against dark background. Axis labels in light ink. Tick labels in muted #B8B7B0. No dark-on-dark failures — all text is light-colored and fully legible. Axis lines in muted light gray.
+      Data: Colors identical to light render — stems and markers remain #009E73. Baseline visible in lighter gray tone. Same data representation as light render.
+      Legibility verdict: PASS
+  criteria_checklist:
+    visual_quality:
+      score: 29
+      max: 30
+      items:
+      - id: VQ-01
+        name: Text Legibility
+        score: 8
+        max: 8
+        passed: true
+        comment: Title 24pt, axis labels 20pt, tick labels 16pt — all explicitly set
+          and readable in both themes
+      - id: VQ-02
+        name: No Overlap
+        score: 6
+        max: 6
+        passed: true
+        comment: 30 well-spaced stems, no text collisions
+      - id: VQ-03
+        name: Element Visibility
+        score: 6
+        max: 6
+        passed: true
+        comment: Stems (size=0.9) and markers (size=4) appropriately sized for 30
+          points; baseline clearly visible
+      - id: VQ-04
+        name: Color Accessibility
+        score: 2
+        max: 2
+        passed: true
+        comment: 'Single brand green #009E73, CVD-safe, good contrast in both themes'
+      - id: VQ-05
+        name: Layout & Canvas
+        score: 4
+        max: 4
+        passed: true
+        comment: 16:9 canvas, balanced margins, plot fills canvas well
+      - id: VQ-06
+        name: Axis Labels & Title
+        score: 1
+        max: 2
+        passed: false
+        comment: Y-axis 'Amplitude' is descriptive but lacks units/context; 'Amplitude
+          (normalized)' would be better
+      - id: VQ-07
+        name: Palette Compliance
+        score: 2
+        max: 2
+        passed: true
+        comment: 'First series is #009E73; backgrounds #FAF8F1 (light) and #1A1A17
+          (dark); theme chrome adapts correctly'
+    design_excellence:
+      score: 10
+      max: 20
+      items:
+      - id: DE-01
+        name: Aesthetic Sophistication
+        score: 4
+        max: 8
+        passed: true
+        comment: Clean, well-configured with brand color and baseline; above generic
+          defaults but not publication-ready
+      - id: DE-02
+        name: Visual Refinement
+        score: 4
+        max: 6
+        passed: true
+        comment: Y-axis-only grid at 10% opacity is excellent; x-axis grid suppressed;
+          theme_minimal removes top/right spines
+      - id: DE-03
+        name: Data Storytelling
+        score: 2
+        max: 6
+        passed: false
+        comment: Data displayed but decay pattern not visually emphasized; no visual
+          hierarchy or storytelling
+    spec_compliance:
+      score: 15
+      max: 15
+      items:
+      - id: SC-01
+        name: Plot Type
+        score: 5
+        max: 5
+        passed: true
+        comment: Correct stem plot via geom_segment + geom_point + geom_hline
+      - id: SC-02
+        name: Required Features
+        score: 4
+        max: 4
+        passed: true
+        comment: Thin stems, visible circular markers, y=0 baseline, consistent sizing
+      - id: SC-03
+        name: Data Mapping
+        score: 3
+        max: 3
+        passed: true
+        comment: Sample index on x, amplitude on y; all 30 points visible
+      - id: SC-04
+        name: Title & Legend
+        score: 3
+        max: 3
+        passed: true
+        comment: Title 'stem-basic · plotnine · anyplot.ai' correct; no legend appropriate
+          for single series
+    data_quality:
+      score: 15
+      max: 15
+      items:
+      - id: DQ-01
+        name: Feature Coverage
+        score: 6
+        max: 6
+        passed: true
+        comment: Shows positive AND negative values, oscillation, and decay envelope
+          — all stem plot characteristics
+      - id: DQ-02
+        name: Realistic Context
+        score: 5
+        max: 5
+        passed: true
+        comment: Damped sinusoidal signal is a textbook signal processing example;
+          neutral and scientific
+      - id: DQ-03
+        name: Appropriate Scale
+        score: 4
+        max: 4
+        passed: true
+        comment: 30 samples, normalized amplitude range, physically plausible decay
+          constant and frequency
+    code_quality:
+      score: 10
+      max: 10
+      items:
+      - id: CQ-01
+        name: KISS Structure
+        score: 3
+        max: 3
+        passed: true
+        comment: Clean 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
+      - id: CQ-03
+        name: Clean Imports
+        score: 2
+        max: 2
+        passed: true
+        comment: All 11 plotnine imports are used
+      - id: CQ-04
+        name: Code Elegance
+        score: 2
+        max: 2
+        passed: true
+        comment: Pythonic, appropriate complexity, no over-engineering
+      - id: CQ-05
+        name: Output & API
+        score: 1
+        max: 1
+        passed: true
+        comment: Saves as plot-{THEME}.png, current API throughout
+    library_mastery:
+      score: 8
+      max: 10
+      items:
+      - id: LM-01
+        name: Idiomatic Usage
+        score: 5
+        max: 5
+        passed: true
+        comment: 'Fully idiomatic grammar of graphics: layered geoms, aes() mappings,
+          theme() customization'
+      - id: LM-02
+        name: Distinctive Features
+        score: 3
+        max: 5
+        passed: true
+        comment: Composing stem plot from primitive geoms (geom_segment + geom_point
+          + geom_hline) demonstrates grammar-of-graphics thinking; somewhat library-specific
+          but not exceptional
+  verdict: APPROVED
+impl_tags:
+  dependencies: []
+  techniques:
+  - layer-composition
+  patterns:
+  - data-generation
+  dataprep: []
+  styling:
+  - grid-styling