feat(highcharts): implement line-yield-curve

[github-actions]

Implementation: line-yield-curve - javascript/highcharts

Implements the javascript/highcharts version of line-yield-curve.

File: plots/line-yield-curve/implementations/javascript/highcharts.js

Parent Issue: #4664

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

Light render (plot-light.png): Three U.S. Treasury yield curves plotted on a warm off-white #FAF8F1 background. X-axis shows maturity labels (1M through 30Y) on log-transformed positions; Y-axis shows Yield (%) from 0.0% to 6.0%. First series (Jan 2021 — Normal) is brand green #009E73 showing a classic upward-sloping curve from near-zero short rates to ~1.8% at 30Y. Second series (Nov 2022 — Inverted) is lavender #C475FD showing high rates (3.4–4.8%) with short rates exceeding long rates. Third series (Jun 2024 — Flat) is blue #4467A3 showing a high flat-to-slightly-inverted shape (~5.3% short, ~4.3% long). A light pink plot band spans 1M–2Y labeled "Inversion zone" in italic text. Legend is top-right with colored markers and descriptive names. Title, axis labels, and tick labels are all dark text — clearly readable against the light background.

Dark render (plot-dark.png): Same chart on a warm near-black #1A1A17 background. All three data series colors are identical to the light render (green, lavender, blue — Imprint palette unchanged). Chrome elements have flipped correctly: title, axis labels, tick labels, and legend text are all rendered in light colors against the dark background — no dark-on-dark failures detected. The inversion zone plot band uses a darker reddish tint (rgba(174,48,48,0.15)) that remains visible. Grid lines are subtle, readable, and correctly adapt to the dark surface. All text is legible.

Both paragraphs are required. A review that only describes one render is invalid.

Score: 91/100

Category	Score	Max
Visual Quality	29	30
Design Excellence	13	20
Spec Compliance	15	15
Data Quality	15	15
Code Quality	10	10
Library Mastery	9	10
Total	91	100

Visual Quality (29/30)

• VQ-01: Text Legibility (7/8) — All fonts explicitly set and readable in both themes; minor deduction for "Inversion zone" band label at 11px CSS, which is below the recommended minimum (~13px) and appears slightly small
• VQ-02: No Overlap (6/6) — No text or element collisions in either render
• VQ-03: Element Visibility (6/6) — Lines and markers well-proportioned for 11 data points per series; lineWidth 2.5 and marker radius 5 are appropriate
• VQ-04: Color Accessibility (2/2) — Imprint palette provides good CVD-safe hue separation across green/lavender/blue
• VQ-05: Layout & Canvas (4/4) — Plot fills canvas well, balanced margins, legend top-right doesn't interfere with data; no content clipped
• VQ-06: Axis Labels & Title (2/2) — "Yield (%)" with units, "Maturity" descriptive; custom tick formatter shows meaningful labels
• VQ-07: Palette Compliance (2/2) — First series #009E73, second #C475FD, third #4467A3 — Imprint canonical order; t.palette used; transparent background lets themed page surface show through; text and grid via t.ink/t.inkSoft/t.grid tokens; correct in both renders

Design Excellence (13/20)

• DE-01: Aesthetic Sophistication (5/8) — Above "well-configured default": plot band highlighting inversion zone and descriptive curve labels add narrative sophistication. Doesn't quite reach "clearly above defaults" territory — styled legend and plot band fall short of FiveThirtyEight-level polish
• DE-02: Visual Refinement (4/6) — X-axis gridlines suppressed (gridLineColor: "transparent"), Y-axis grid uses subtle themed token, legend has rounded corners and theme-matched border, italic "Inversion zone" label shows attention to detail
• DE-03: Data Storytelling (4/6) — Three curves explicitly labeled "Normal", "Inverted", "Flat" with dates; plot band creates a focal point at the inversion region; viewer immediately grasps the economic narrative. Strong visual hierarchy for a yield curve chart

Spec Compliance (15/15)

• SC-01: Plot Type (5/5) — Correct multi-series line chart for yield curves
• SC-02: Required Features (4/4) — Log-spaced x-axis positioning (via log10 transform), maturity labels on ticks, ≥2 curves showing curve shape evolution, inversion region highlighted with shaded band and label, legend with date labels
• SC-03: Data Mapping (3/3) — maturity_years values used for x positioning (log-transformed), maturity labels on ticks, yield % on Y; all 11 maturity points per curve shown
• SC-04: Title & Legend (3/3) — Title "U.S. Treasury Yield Curves · line-yield-curve · javascript · highcharts · anyplot.ai" follows the {Descriptive Title} · {spec-id} · {language} · {library} · anyplot.ai format; legend labels correctly describe date and curve shape

Data Quality (15/15)

• DQ-01: Feature Coverage (6/6) — All three canonical yield curve shapes represented: normal (upward-sloping Jan 2021), inverted (Nov 2022 rate hike peak), flat (Jun 2024 higher-for-longer)
• DQ-02: Realistic Context (5/5) — Real U.S. Treasury yield curve data from three distinct macroeconomic regimes; neutral financial topic
• DQ-03: Appropriate Scale (4/4) — Jan 2021 near-zero rates (0.04–1.83%), Nov 2022 inversion peak (3.42–4.75%), Jun 2024 flat high rates (4.28–5.38%) — all factually accurate for those periods

Code Quality (10/10)

• CQ-01: KISS Structure (3/3) — Data arrays → log transform → Highcharts.chart() call; toPoints is a one-liner expression, not a function
• CQ-02: Reproducibility (2/2) — All data hardcoded; fully deterministic
• CQ-03: Clean Imports (2/2) — No imports; all globals (window.ANYPLOT_TOKENS, window.ANYPLOT_THEME, Highcharts) are used
• CQ-04: Code Elegance (2/2) — Clean, no over-engineering; comment explaining log transform rationale is appropriately placed
• CQ-05: Output & API (1/1) — Highcharts.chart("container", ...) with animation: false on both chart and series; credits: { enabled: false }; no explicit width/height

Library Mastery (9/10)

• LM-01: Idiomatic Usage (5/5) — Expert use of window.ANYPLOT_TOKENS for full theme-adaptive chrome; plotBands with label; custom formatter functions for ticks and tooltip; legend styling with backgroundColor/borderColor/borderRadius
• LM-02: Distinctive Features (4/5) — plotBands with theme-adaptive alpha for highlighting (Highcharts-distinctive); custom tickPositions array with formatter to map log-scale back to labels; tooltip formatter with maturity resolution — strong Highcharts-specific feature use; stops just short of 5 (e.g., no plotLines or renderer usage)

Score Caps Applied

• None — no caps triggered

Strengths

• Accurate historical U.S. Treasury data covering three distinct rate environments (COVID near-zero, rate-hike inversion, higher-for-longer flat)
• Clever log10 x-axis transform with custom maturity tick formatter — correctly reflects the non-linear time spacing of bond maturities
• Theme-adaptive inversion zone plot band with correct alpha for light and dark surfaces
• Perfect Imprint palette compliance: brand green first, canonical order, t.palette for all series
• All spec-required features implemented: log-spaced axis, custom tick labels, multi-curve comparison, inversion highlighting, dated legend

Weaknesses

• "Inversion zone" band label at fontSize: "11px" is below the recommended minimum (~13px) — appears slightly small in both renders; increase to 13px for consistency with tick labels

Issues Found

1. VQ-01 MINOR: "Inversion zone" plot band label at 11px CSS is slightly below the safe minimum
   • Fix: Change fontSize: "11px" to fontSize: "13px" in the plotBands label style

AI Feedback for Next Attempt

The implementation is publication-quality. If repair is triggered, focus only on the "Inversion zone" label size (11px → 13px). Design excellence is solid at 13/20; the chart successfully tells the yield-curve story through visual hierarchy. No structural changes needed.

Verdict: APPROVED