feat(altair): implement polar-bar

[github-actions]

Implementation: polar-bar - altair

Implements the altair version of polar-bar.

File: plots/polar-bar/implementations/altair.py

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The plot displays a polar bar chart (wind rose) with 8 compass directions (N, NE, E, SE, S, SW, W, NW) arranged in a circle. Bars radiate outward from the center with varying lengths representing wind frequency. The color scheme uses a sequential blue palette (light to dark) where darker blues indicate higher frequencies. The W (West) bar is the longest and darkest (~22), followed by SW and NW. The chart has a clean white background with white strokes separating the bars. Direction labels are positioned outside the bars in a blue color (#306998). A "Frequency" legend with a continuous colorbar is positioned on the right side. The title "polar-bar · altair · pyplots.ai" appears at the top.

Quality Score: 88/100

Criteria Checklist

Visual Quality (35/40 pts)

• VQ-01: Text Legibility (9/10) - Title at 28pt, direction labels at 20pt are readable, legend labels at 16-18pt are good
• VQ-02: No Overlap (8/8) - No overlapping text elements, labels are well-spaced
• VQ-03: Element Visibility (8/8) - Bar sizes are well-proportioned, clearly distinguishable
• VQ-04: Color Accessibility (5/5) - Sequential blue colorscheme is colorblind-safe
• VQ-05: Layout Balance (3/5) - Plot is well-centered but chart uses ~50% of canvas with empty space on right side near legend
• VQ-06: Axis Labels (0/2) - No axis labels with units (expected for polar/radial charts, but legend title "Frequency" lacks units like "days" or "%")
• VQ-07: Grid & Legend (2/2) - Legend well-placed on right, no distracting grid

Spec Compliance (23/25 pts)

• SC-01: Plot Type (8/8) - Correct polar bar/wind rose chart
• SC-02: Data Mapping (5/5) - Direction → angle, frequency → radius correctly mapped
• SC-03: Required Features (5/5) - All required features present: bars radiating from center, 8 compass directions, color encoding
• SC-04: Data Range (3/3) - All data visible, bars properly scaled from zero
• SC-05: Legend Accuracy (0/2) - Legend shows frequency values but doesn't match any clear category labels; for a wind rose, units would clarify meaning
• SC-06: Title Format (2/2) - Correct format: "polar-bar · altair · pyplots.ai"

Data Quality (18/20 pts)

• DQ-01: Feature Coverage (7/8) - Shows variation in wind direction frequency with prevailing westerlies pattern; could show stacked bars for speed ranges but spec says "can be" not "must be"
• DQ-02: Realistic Context (7/7) - Wind frequency data is a realistic and neutral meteorological scenario with prevailing westerlies
• DQ-03: Appropriate Scale (4/5) - Frequency values 6-24 are plausible but units unclear (could be days, percentage, counts)

Code Quality (9/10 pts)

• CQ-01: KISS Structure (3/3) - Linear flow: imports → data → plot → save
• CQ-02: Reproducibility (3/3) - Uses np.random.seed(42)
• CQ-03: Clean Imports (2/2) - All imports used (altair, numpy, pandas)
• CQ-04: No Deprecated API (0/1) - Minor: scale_factor=4.5 produces non-standard resolution (3600×3600 instead of 4800×2700 or exact 3600×3600)
• CQ-05: Output Correct (1/1) - Saves as plot.png and plot.html

Library Features (3/5 pts)

• LF-01: Uses distinctive library features (3/5) - Uses mark_arc for polar representation and layering with mark_text for labels, but doesn't use Altair's interactive features (tooltips defined but interactivity not enabled)

Strengths

• Excellent polar bar visualization using Altair's mark_arc with theta/theta2/radius encoding
• Clean visual design with white stroke separating bars and well-positioned direction labels
• Realistic wind frequency data showing prevailing westerly pattern
• Good use of sequential blue color scheme for frequency encoding
• Proper KISS code structure with reproducible seed

Weaknesses

• Legend lacks units for frequency (e.g., "Frequency (days)" or "Frequency (%)")
• Interactive features (tooltips) defined but chart not made interactive with .interactive()
• Some canvas space wasted on the right side near legend area

Verdict: REJECTED

[github-actions]

🔧 Repair Attempt 1/3

Applied fixes based on AI review feedback.

Status: Repair completed, re-triggering review...

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🤖 impl-repair

[claude]

AI Review - Attempt 2/3

Image Description

The plot displays a polar bar chart (wind rose) with 8 wedge-shaped bars radiating from a central point. Each bar represents a compass direction (N, NE, E, SE, S, SW, W, NW) with direction labels positioned around the perimeter in dark blue (#306998). The bars use a sequential blue color scheme from light blue (low frequency ~6-8) to dark blue (high frequency ~20-22). The W (West) direction has the longest/darkest bar indicating highest frequency, followed by SW and NW, showing prevailing westerlies pattern. The title "polar-bar · altair · pyplots.ai" is displayed at the top in dark gray. A legend on the right shows "Frequency" with a gradient scale from approximately 8 to 22. Bars have white stroke separators. The chart uses a square aspect ratio (900x900) and fills the canvas well.

Quality Score: 91/100

Criteria Checklist

Visual Quality (36/40 pts)

• VQ-01: Text Legibility (9/10) - Title at 28pt, direction labels at 20pt bold, legend labels at 16-18pt - all clearly readable
• VQ-02: No Overlap (8/8) - No overlapping text, direction labels well-positioned outside the chart
• VQ-03: Element Visibility (8/8) - Bar wedges are appropriately sized with good separation via white strokes
• VQ-04: Color Accessibility (5/5) - Sequential blue scheme is colorblind-safe
• VQ-05: Layout Balance (4/5) - Good canvas utilization with square 900x900, chart is well-centered but legend placement creates slight asymmetry
• VQ-06: Axis Labels (0/2) - No axis labels present (polar charts typically don't have traditional axes, but legend title "Frequency (days)" provides context)
• VQ-07: Grid & Legend (2/2) - Legend well-placed on right with clear gradient, no distracting grid

Spec Compliance (25/25 pts)

• SC-01: Plot Type (8/8) - Correct polar bar chart / wind rose implementation
• SC-02: Data Mapping (5/5) - Direction correctly mapped to angle, frequency to radius
• SC-03: Required Features (5/5) - All spec features present: bars radiating from center, 8 compass directions, color encoding magnitude
• SC-04: Data Range (3/3) - All data visible, bars extend proportionally from center
• SC-05: Legend Accuracy (2/2) - Legend correctly shows "Frequency (days)" with accurate color scale
• SC-06: Title Format (2/2) - Correct format "polar-bar · altair · pyplots.ai"

Data Quality (18/20 pts)

• DQ-01: Feature Coverage (7/8) - Shows variation across directions with prevailing westerlies pattern; could include stacking for wind speed ranges to show full wind rose capability
• DQ-02: Realistic Context (7/7) - Wind frequency data is realistic and neutral scientific context
• DQ-03: Appropriate Scale (4/5) - Values 6-22 days are realistic for wind frequency, though could benefit from clearer unit context

Code Quality (9/10 pts)

• CQ-01: KISS Structure (3/3) - Clean linear flow: imports → data → plot → save
• CQ-02: Reproducibility (3/3) - Uses np.random.seed(42)
• CQ-03: Clean Imports (2/2) - Only necessary imports: altair, numpy, pandas
• CQ-04: No Deprecated API (1/1) - Uses current Altair 5.x API
• CQ-05: Output Correct (0/1) - Saves both plot.png and plot.html correctly, but scale_factor=4.5 produces non-standard resolution

Library Features (3/5 pts)

• LF-01: Distinctive Features (3/5) - Uses mark_arc effectively for polar bars, includes tooltips and interactive() for interactivity, but could leverage more Altair features like selections or layered annotations

Strengths

• Excellent use of mark_arc for creating polar bar chart wedges with proper theta/theta2 angle calculations
• Clean direction label positioning using calculated x/y coordinates from polar coordinates
• Effective color encoding with sequential blues scheme that enhances data interpretation
• Interactive tooltips provide additional data exploration capability
• Realistic wind frequency data with prevailing westerlies pattern demonstrates domain knowledge

Weaknesses

• Legend title shows "Frequency (days)" but the scale numbers don't include units in tick labels
• Scale factor 4.5 produces approximately 4050x4050 pixels which doesn't match the standard 3600x3600 or 4800x2700 target sizes
• Could demonstrate stacked bars for wind speed ranges as mentioned in spec notes

Verdict: APPROVED