feat(plotnine): implement spectrogram-basic

[github-actions]

Implementation: spectrogram-basic - plotnine

Implements the plotnine version of spectrogram-basic.

File: plots/spectrogram-basic/implementations/plotnine.py

Parent Issue: #2927

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The spectrogram displays a time-frequency heatmap on a 16:9 canvas with a clean minimal theme. The x-axis shows "Time (s)" ranging from 0.0 to 2.0 seconds, and the y-axis shows "Frequency (Hz)" ranging from 0 to 500 Hz. A colorbar on the right labeled "Power (dB)" shows the scale from approximately -70 dB (dark blue) to -20 dB (light yellow/cream). The plot clearly shows a chirp signal with frequency increasing linearly from about 50 Hz at t=0 to about 200 Hz at t=2, visible as a bright diagonal band sweeping upward across the time axis. The background noise appears as a mottled blue-green pattern at frequencies outside the chirp. The title "spectrogram-basic · plotnine · pyplots.ai" is displayed at the top.

Quality Score: 91/100

Criteria Checklist

Visual Quality (37/40 pts)

• VQ-01: Text Legibility (10/10) - Title, axis labels, and tick labels are all clearly readable at appropriate sizes
• VQ-02: No Overlap (8/8) - No overlapping text elements
• VQ-03: Element Visibility (7/8) - Tiles are visible and the chirp pattern is clear, though some granularity in the high-frequency region
• VQ-04: Color Accessibility (5/5) - Uses a perceptually reasonable colormap that avoids red-green issues
• VQ-05: Layout Balance (5/5) - Good use of canvas space with balanced margins
• VQ-06: Axis Labels (2/2) - Labels include units: "Time (s)" and "Frequency (Hz)"
• VQ-07: Grid & Legend (0/2) - No visible grid (spec suggests grid could help), legend is well-placed

Spec Compliance (25/25 pts)

• SC-01: Plot Type (8/8) - Correct spectrogram heatmap visualization
• SC-02: Data Mapping (5/5) - Time on X, Frequency on Y, Power as color intensity
• SC-03: Required Features (5/5) - Colorbar with dB units, clear axes, chirp signal demonstration
• SC-04: Data Range (3/3) - Shows full 0-2s time range and 0-500 Hz frequency range
• SC-05: Legend Accuracy (2/2) - Colorbar correctly labeled "Power (dB)"
• SC-06: Title Format (2/2) - Correctly uses "{spec-id} · {library} · pyplots.ai" format

Data Quality (17/20 pts)

• DQ-01: Feature Coverage (7/8) - Shows time-frequency representation well; chirp clearly visible; noise background present
• DQ-02: Realistic Context (7/7) - Chirp signal is a standard signal processing example, scientifically neutral
• DQ-03: Appropriate Scale (3/5) - Sample rate and frequency ranges are plausible; filtering to 500 Hz is arbitrary when chirp only goes to 200 Hz

Code Quality (10/10 pts)

• CQ-01: KISS Structure (3/3) - Simple linear flow: imports → data → plot → save
• CQ-02: Reproducibility (3/3) - Uses np.random.seed(42)
• CQ-03: Clean Imports (2/2) - All imports are used
• CQ-04: No Deprecated API (1/1) - Uses current APIs
• CQ-05: Output Correct (1/1) - Saves as plot.png

Library Features (2/5 pts)

• LF-01: Uses distinctive library features (2/5) - Uses geom_tile appropriately for heatmap, but custom color gradient instead of plotnine's scale functions; theme_minimal is good but basic usage overall

Strengths

• Clear visualization of chirp signal with frequency increasing over time
• Proper use of dB scale for power representation
• Well-formatted title following spec format exactly
• Good axis labels with units as specified
• Reproducible with fixed random seed
• Clean, readable KISS code structure
• Appropriate colormap that is perceptually reasonable

Weaknesses

• Custom color gradient could use a more perceptually uniform colormap like viridis (spec recommends viridis/inferno)
• No grid lines to aid in reading specific time-frequency values
• Frequency axis filtered to 500 Hz when chirp only reaches 200 Hz - could be tighter range for better visualization

Verdict: APPROVED