feat(letsplot): implement phase-diagram

[github-actions]

Implementation: phase-diagram - letsplot

Implements the letsplot version of phase-diagram.

File: plots/phase-diagram/implementations/letsplot.py

Parent Issue: #3004

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The plot displays a phase diagram (state space plot) showing four spiral trajectories converging to a fixed point at the origin. The trajectories are colored in blue, yellow, green, and purple, each starting from different initial conditions marked with hollow circle markers. The fixed point (equilibrium) at the origin is marked with a bold red "X". The x-axis is labeled "Position (x)" ranging from approximately -2.5 to 3, and the y-axis is labeled "Velocity (dx/dt)" ranging from approximately -6 to 5. The title "phase-diagram · letsplot · pyplots.ai" appears at the top. A legend on the right side shows "Starting Condition" with four entries corresponding to each trajectory's initial (x, v) values. The plot has a clean minimal theme with subtle gray grid lines.

Quality Score: 93/100

Criteria Checklist

Visual Quality (37/40 pts)

• VQ-01: Text Legibility (10/10) - Title, axis labels, tick marks, and legend text are all clearly readable at appropriate sizes
• VQ-02: No Overlap (8/8) - No overlapping text elements; all labels and legend entries are clearly separated
• VQ-03: Element Visibility (7/8) - Trajectory lines are well-sized with good alpha (0.8), starting points clearly marked; minor deduction as some inner spiral loops are slightly dense
• VQ-04: Color Accessibility (5/5) - Uses blue, yellow, green, purple palette which is colorblind-friendly; good contrast between all colors
• VQ-05: Layout Balance (5/5) - Plot fills canvas well with balanced margins; legend positioned appropriately on right
• VQ-06: Axis Labels (2/2) - Descriptive labels with proper notation: "Position (x)" and "Velocity (dx/dt)"
• VQ-07: Grid & Legend (0/2) - Grid is visible and subtle, but legend title "Starting Condition" is slightly generic; legend entries could be more descriptive

Spec Compliance (25/25 pts)

• SC-01: Plot Type (8/8) - Correct phase diagram showing x vs dx/dt trajectories
• SC-02: Data Mapping (5/5) - Position correctly mapped to x-axis, velocity (derivative) to y-axis
• SC-03: Required Features (5/5) - Shows multiple trajectories, fixed point marked, spiral convergence visible, direction of time evolution implied by path
• SC-04: Data Range (3/3) - All data points visible within axes range
• SC-05: Legend Accuracy (2/2) - Legend correctly identifies each trajectory by initial condition
• SC-06: Title Format (2/2) - Correct format: "phase-diagram · letsplot · pyplots.ai"

Data Quality (18/20 pts)

• DQ-01: Feature Coverage (7/8) - Shows spiral convergence (damped system), multiple initial conditions, equilibrium point; could show a limit cycle or undamped case for contrast
• DQ-02: Realistic Context (7/7) - Damped harmonic oscillator is a classic physics example; neutral scientific context
• DQ-03: Appropriate Scale (4/5) - Values are physically reasonable for a normalized oscillator; omega=2, gamma=0.3 produce sensible dynamics

Code Quality (10/10 pts)

• CQ-01: KISS Structure (3/3) - Clean linear flow: imports → data generation → plot → save
• CQ-02: Reproducibility (3/3) - np.random.seed(42) set (though not actually used since data is deterministic)
• CQ-03: Clean Imports (2/2) - All imports are used (numpy, pandas, lets_plot)
• CQ-04: No Deprecated API (1/1) - Uses current lets-plot API
• CQ-05: Output Correct (1/1) - Saves as plot.png and plot.html

Library Features (3/5 pts)

• LF-01: Uses lets-plot features (3/5) - Uses ggplot grammar, geom_path for trajectories, geom_point with shape/stroke for markers, scale_color_manual, theme_minimal with customization; could leverage more lets-plot specific interactive features

Strengths

• Excellent visualization of damped harmonic oscillator phase space with clear spiral convergence to equilibrium
• Multiple trajectories from different initial conditions effectively demonstrate basin of attraction concept
• Fixed point clearly marked with distinctive red X marker
• Starting points clearly marked with hollow circles with stroke, making trajectory origins easy to identify
• Clean, professional styling with appropriate color palette and readable text at all sizes
• Proper use of lets-plot grammar of graphics (ggplot, geom_path, aes mappings)

Weaknesses

• Legend entries show raw initial condition tuples; more descriptive labels like "High displacement" or "Mixed initial" would improve readability
• Inner spiral loops become slightly dense near the equilibrium point; consider using direction arrows (geom_segment) to show time evolution more clearly

Verdict: APPROVED