feat(ggplot2): implement horizon-basic

[github-actions]

Implementation: horizon-basic - r/ggplot2

Implements the r/ggplot2 version of horizon-basic.

File: plots/horizon-basic/implementations/r/ggplot2.R

Parent Issue: #1877

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

Light render (plot-light.png): Warm off-white background (#FAF8F1-consistent). Bold dark title "horizon-basic · r · ggplot2 · anyplot.ai" top-left, medium-grey subtitle explaining the z-score/3-band folding below it, 8 dark-grey service-name labels down the left (api-gateway, auth-service, payment-svc, search-index, user-profile, notification, cache-layer, recommender), "Date" axis title and Jun 02/04/06/08 tick labels along the bottom, tertiary caption explaining the blue/red + shade-depth encoding at the very bottom. Each lane shows a jagged horizon silhouette built from stacked blue (#4467A3-family) and red (#AE3030-family) ribbons with three visible intensity steps. All text is clearly readable against the light background — no light-on-light issues.

Dark render (plot-dark.png): Warm near-black background (#1A1A17-consistent). Identical layout; title/subtitle/axis-text/caption all switch to light off-white/grey tones and remain fully legible — no dark-on-dark failures (checked labels, ticks, caption). Data colors (blue/red bands) are pixel-identical to the light render — only chrome flipped, confirming correct theme-adaptive implementation.

Both paragraphs confirmed — legibility PASS in both themes.

Score: 89/100

Category	Score	Max
Visual Quality	28	30
Design Excellence	15	20
Spec Compliance	15	15
Data Quality	14	15
Code Quality	10	10
Library Mastery	7	10
Total	89	100

Visual Quality (28/30)

• VQ-01: Text Legibility (7/8) - Explicit sizes throughout, readable both themes, no overflow/clipping
• VQ-02: No Overlap (6/6) - No overlap anywhere
• VQ-03: Element Visibility (5/6) - Lowest alpha band (0.35) is a bit subtle against the light page background
• VQ-04: Color Accessibility (2/2) - Blue/matte-red pairing is CVD-safe
• VQ-05: Layout & Canvas (4/4) - Fills canvas well, balanced margins, nothing cut off
• VQ-06: Axis Labels & Title (2/2) - "Date" + descriptive subtitle/caption stating the encoding
• VQ-07: Palette Compliance (2/2) - Correctly uses imprint_div diverging endpoints for the continuous baseline-deviation encoding; theme-correct chrome both renders

Design Excellence (15/20)

• DE-01: Aesthetic Sophistication (6/8) - Thoughtful diverging-palette semantics and a well-executed horizon-fold technique, above configured-default but short of full publication polish
• DE-02: Visual Refinement (5/6) - Grid removed, spines minimal, subtle lane dividers; margins slightly tight (10-16pt @ dpi=400)
• DE-03: Data Storytelling (4/6) - Alpha intensity creates hierarchy drawing the eye to spikes, but no explicit callout highlights the standout anomaly

Spec Compliance (15/15)

• SC-01: Plot Type (5/5) - Genuine horizon chart via folded, layered ribbon bands
• SC-02: Required Features (4/4) - 3 bands, mirrored pos/neg coloring, meaningful zero baseline, magnitude-driven intensity, 8 series
• SC-03: Data Mapping (3/3) - X=date, Y=lane per series, color=folded magnitude
• SC-04: Title & Legend (3/3) - Title exactly matches mandated format; series names serve as per-lane legend

Data Quality (14/15)

• DQ-01: Feature Coverage (5/6) - Shows all 3 bands incl. full-saturation spikes; not every series exhibits every band depth equally
• DQ-02: Realistic Context (5/5) - Neutral, plausible microservice CPU-monitoring scenario
• DQ-03: Appropriate Scale (4/4) - Z-scored trend+noise+spike data is well-scaled

Code Quality (10/10)

• CQ-01: KISS Structure (3/3) - Linear imports -> data -> fold -> plot -> save
• CQ-02: Reproducibility (2/2) - set.seed(42)
• CQ-03: Clean Imports (2/2) - ggplot2, dplyr, scales, ragg all used
• CQ-04: Code Elegance (2/2) - Clean vectorized fold logic, no fake UI
• CQ-05: Output & API (1/1) - ggsave via ragg::agg_png, correct dims/dpi

Library Mastery (7/10)

• LM-01: Idiomatic Usage (4/5) - Idiomatic layered geom_ribbon + scale/theme system usage
• LM-02: Distinctive Features (3/5) - Creative layer-composition to build a horizon chart, though the technique is replicable in other grammar-of-graphics-style libraries

Score Caps Applied

• None

Strengths

• Correct, idiomatic horizon-chart folding technique: geom_ribbon layers with per-band alpha (0.35/0.65/1.0) faithfully encode magnitude within each of the 3 folded bands per polarity
• Correct semantic use of the Imprint diverging colormap endpoints (#AE3030 matte red / #4467A3 blue) for below/above-baseline deviation — matches imprint_div guidance exactly
• Both themes render correctly: theme-adaptive chrome, identical data colors between light and dark
• Clean, reproducible, KISS-structured code with set.seed(42) and no fake functionality
• Realistic, neutral 8-microservice CPU-deviation dataset that exercises all 3 fold bands including saturated spikes
• No text overlap or edge clipping in either render; mandated title format reproduced exactly

Weaknesses

• Design Excellence/storytelling is competent but not exceptional: no annotation/callout highlights the most notable anomaly (e.g. the fully-saturated auth-service spike) — would raise DE-03
• VQ-03: the lightest band (alpha=0.35) is subtle against #FAF8F1 for near-baseline deviations — consider nudging the lowest alpha up slightly (e.g. 0.42-0.48) for better separation without disturbing deep-band contrast
• plot.margin = margin(10, 16, 10, 10) is quite tight at dpi=400 (~55-90 source px on a 3200x1800 canvas); not clipped, but more generous margins (especially top-right) would add polish
• No small legend/swatch maps the 3 discrete alpha steps to an approximate z-score range — the caption states "deeper shade means a larger deviation" but doesn't give a reader a concrete scale reference

Issues Found

1. DE-03 LOW: No visual callout on the standout anomaly
   • Fix: Add a small annotation/label pointing at the most extreme spike (e.g. the saturated auth-service dip) to give the chart a clear focal point
2. VQ-03 MINOR: Lightest band alpha too close to background in light theme
   • Fix: Raise the lowest-band alpha from 0.35 to ~0.42-0.48
3. DE-02 MINOR: Tight plot margins
   • Fix: Increase plot.margin (e.g. margin(16, 20, 12, 12)) for more breathing room

AI Feedback for Next Attempt

Strong implementation overall — the horizon-fold technique and diverging-palette semantics are correct and well executed. To push past 90: add a small annotation/callout highlighting the most extreme deviation for a clearer storytelling focal point, slightly raise the lowest band's alpha for better separation from the light-theme background, and loosen plot.margin a bit for extra polish. These are refinements, not correctness issues.

Verdict: REJECTED