feat(letsplot): implement scatter-regression-lowess

[github-actions]

Implementation: scatter-regression-lowess - letsplot

Implements the letsplot version of scatter-regression-lowess.

File: plots/scatter-regression-lowess/implementations/letsplot.py

Parent Issue: #2855

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The plot displays a scatter plot with approximately 200 blue data points (#306998) representing plant growth rate vs temperature. A smooth yellow LOWESS curve (#FFD43B) is overlaid with a light yellow confidence band (se=True). The curve shows a clear non-linear relationship: growth rate increases from ~17 cm/day at 5°C to a peak of ~22 cm/day around 15-17°C, then gradually declines back to ~18 cm/day at 40°C. The title "scatter-regression-lowess · letsplot · pyplots.ai" is properly formatted at the top. Axis labels include units: "Temperature (°C)" and "Growth Rate (cm/day)". The minimal theme provides a clean white background with subtle gray grid lines. Points have appropriate alpha (0.6) showing density while allowing the LOWESS curve to be clearly visible.

Quality Score: 93/100

Criteria Checklist

Visual Quality (38/40 pts)

• VQ-01: Text Legibility (10/10) - Title, axis labels, and tick marks all clearly readable at full size with appropriate font sizes (24pt title, 20pt axis labels, 16pt ticks)
• VQ-02: No Overlap (8/8) - No overlapping text elements, all labels clearly separated
• VQ-03: Element Visibility (7/8) - Points well-sized (size=4) with good alpha (0.6), LOWESS line clearly visible (size=2.5). Minor deduction: some points at edges slightly small relative to canvas
• VQ-04: Color Accessibility (5/5) - Blue points and yellow curve provide excellent contrast, colorblind-safe combination
• VQ-05: Layout Balance (4/5) - Good canvas utilization, plot fills most of the space with balanced margins. Minor whitespace at top
• VQ-06: Axis Labels (2/2) - Descriptive labels with units: "Temperature (°C)" and "Growth Rate (cm/day)"
• VQ-07: Grid & Legend (2/2) - Minimal theme with subtle grid, no legend needed for this single-series plot

Spec Compliance (25/25 pts)

• SC-01: Plot Type (8/8) - Correct scatter plot with LOWESS regression
• SC-02: Data Mapping (5/5) - X=temperature, Y=growth rate correctly mapped
• SC-03: Required Features (5/5) - LOWESS curve distinct from points (solid yellow vs blue), confidence band included, moderate smoothing (span=0.4), appropriate transparency
• SC-04: Data Range (3/3) - Full data range displayed (5-40°C, 14-27 cm/day)
• SC-05: Legend Accuracy (2/2) - No legend needed, single series clearly distinguished by color
• SC-06: Title Format (2/2) - Correctly formatted: "scatter-regression-lowess · letsplot · pyplots.ai"

Data Quality (18/20 pts)

• DQ-01: Feature Coverage (7/8) - Shows non-linear relationship with varying pattern across x-range (rise, peak, decline). Minor: could show more extreme outliers
• DQ-02: Realistic Context (7/7) - Plant growth vs temperature is a real, neutral scientific scenario that naturally exhibits non-linear patterns
• DQ-03: Appropriate Scale (4/5) - Temperature 5-40°C is realistic for plant studies. Growth rate 14-27 cm/day is on the high end but plausible for fast-growing plants

Code Quality (9/10 pts)

• CQ-01: KISS Structure (3/3) - Clean imports → data → plot → save structure, no functions/classes
• CQ-02: Reproducibility (3/3) - np.random.seed(42) set
• CQ-03: Clean Imports (1/2) - All imports used, but some could be condensed (minor)
• 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: Distinctive Features (3/5) - Uses geom_smooth with loess method and se=True for confidence bands, theme_minimal(), element_text() for styling. Good usage but not exceptional

Strengths

• Excellent LOWESS implementation using geom_smooth with loess method and confidence band (se=True)
• Perfect title format and descriptive axis labels with units
• Realistic plant growth vs temperature scenario that naturally demonstrates LOWESS benefits
• Good color contrast between blue points and yellow curve with appropriate transparency
• Clean code structure following KISS principles with reproducible seed

Weaknesses

• Confidence band fill color (#FFD43B) same as line color - could use a lighter/different shade for better visual distinction
• Some imports listed individually could be consolidated (minor style issue)

Verdict: APPROVED