feat(plotnine): implement spectrum-basic

[github-actions]

Implementation: spectrum-basic - plotnine

Implements the plotnine version of spectrum-basic.

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

Parent Issue: #2926

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The plot displays a frequency spectrum on a logarithmic X-axis ranging from 10 Hz to 1000 Hz. The Y-axis shows amplitude in dB, ranging from approximately -80 dB to 0 dB. The plot uses a blue (#306998) line to trace the spectrum. Clear frequency peaks are visible at 50 Hz (fundamental, ~0 dB), 100 Hz (2nd harmonic, ~-5 dB), 150 Hz (3rd harmonic, ~-10 dB), and 500 Hz (high-frequency component, ~-16 dB). The noise floor is visible around -50 to -60 dB with expected fluctuations at higher frequencies. The title "spectrum-basic · plotnine · pyplots.ai" is displayed at the top in bold. Axis labels show "Frequency (Hz)" and "Amplitude (dB)" with proper units. Log tick marks are visible on the X-axis bottom. The background is clean with a minimal theme.

Quality Score: 91/100

Criteria Checklist

Visual Quality (36/40 pts)

• VQ-01: Text Legibility (10/10) - Title is bold 24pt, axis titles 20pt, tick labels 16pt - all clearly readable
• VQ-02: No Overlap (8/8) - No overlapping text elements
• VQ-03: Element Visibility (7/8) - Line is visible and appropriate thickness (1.2), slight deduction as the line could be marginally thicker for the noisy high-frequency region
• VQ-04: Color Accessibility (5/5) - Single blue color with good contrast against white background
• VQ-05: Layout Balance (4/5) - Good proportions, plot fills canvas well; minor margin asymmetry
• VQ-06: Axis Labels (2/2) - Both axes have descriptive labels with units: "Frequency (Hz)" and "Amplitude (dB)"
• VQ-07: Grid & Legend (0/2) - Grid lines are not visible despite panel_grid_major being set; no legend needed for single series but grid should be visible

Spec Compliance (25/25 pts)

• SC-01: Plot Type (8/8) - Correct frequency spectrum line plot
• SC-02: Data Mapping (5/5) - Frequency on X-axis, amplitude on Y-axis correctly assigned
• SC-03: Required Features (5/5) - Logarithmic frequency axis, dB scale amplitude, clear labels with units, identifiable peaks
• SC-04: Data Range (3/3) - Full frequency range (10-1000 Hz) displayed, all data visible
• SC-05: Legend Accuracy (2/2) - N/A for single series, no legend needed
• SC-06: Title Format (2/2) - Correct format: "spectrum-basic · plotnine · pyplots.ai"

Data Quality (20/20 pts)

• DQ-01: Feature Coverage (8/8) - Shows fundamental frequency, harmonics (2nd, 3rd), isolated high-frequency component, and noise floor - demonstrates all aspects of frequency spectrum analysis
• DQ-02: Realistic Context (7/7) - Simulates mechanical vibration signal with motor rotation frequency and harmonics - realistic engineering scenario
• DQ-03: Appropriate Scale (5/5) - FFT with 4096 Hz sample rate, 50 Hz fundamental, dB scale ranging from ~0 to -80 dB - all physically sensible values

Code Quality (10/10 pts)

• CQ-01: KISS Structure (3/3) - Simple script: imports → data generation → FFT → 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) - Current plotnine API
• CQ-05: Output Correct (1/1) - Saves as 'plot.png'

Library Features (0/5 pts)

• LF-01: Uses distinctive library features (0/5) - Uses annotation_logticks which is a nice plotnine feature, but the panel_grid_major=element_text(alpha=0.3) is incorrect syntax (should use element_line not element_text), causing grid lines not to render - this is a code bug that reduces the score

Strengths

• Excellent signal processing implementation with realistic mechanical vibration scenario showing fundamental and harmonics
• Proper use of logarithmic frequency scale with annotation_logticks for professional axis presentation
• Clear axis labels with appropriate units (Hz, dB)
• Good use of dB scale for amplitude visualization as recommended in spec
• Clean KISS code structure with proper FFT computation

Weaknesses

• Grid lines not visible because panel_grid_major=element_text(alpha=0.3) uses wrong element type - should be element_line not element_text

Verdict: APPROVED