feat(altair): implement line-timeseries-rolling

[github-actions]

Implementation: line-timeseries-rolling - altair

Implements the altair version of line-timeseries-rolling.

File: plots/line-timeseries-rolling/implementations/altair.py

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The plot displays a time series of daily temperature data over approximately 6 months (January to late June 2024). It features two overlaid lines: a thin, semi-transparent blue line representing "Raw Data" showing daily fluctuations with considerable noise, and a prominent thicker yellow/gold line representing the "7-Day Rolling Average" that smoothly reveals the underlying seasonal warming trend. The temperature rises from around -2°C in winter to approximately 22°C in early summer. The chart has a white background with subtle dashed grid lines, clear axis labels with units ("Date" and "Temperature (°C)"), and a well-positioned legend in the top-right corner. The title follows the required format.

Quality Score: 93/100

Criteria Checklist

Visual Quality (37/40 pts)

• VQ-01: Text Legibility (10/10) - Title at 28pt, axis labels at 22pt, tick labels at 18pt, all clearly readable
• VQ-02: No Overlap (8/8) - No overlapping text, x-axis date labels are well-spaced
• VQ-03: Element Visibility (7/8) - Lines are well-differentiated with appropriate stroke widths (1.5 vs 4) and opacity (0.5 vs 1.0); raw data could be slightly more visible
• VQ-04: Color Accessibility (5/5) - Blue (#306998) and yellow (#FFD43B) are colorblind-safe, high contrast
• VQ-05: Layout Balance (5/5) - Good use of canvas, balanced margins, plot fills appropriate space
• VQ-06: Axis Labels (2/2) - "Date" and "Temperature (°C)" with units
• VQ-07: Grid & Legend (0/2) - Grid is subtle with dashed style and 0.3 opacity; however legend overlaps with data points in the upper-right area

Spec Compliance (25/25 pts)

• SC-01: Plot Type (8/8) - Correct line chart with two series
• SC-02: Data Mapping (5/5) - Date on X, temperature values on Y
• SC-03: Required Features (5/5) - Raw data with lighter style, rolling average prominent, legend distinguishes series, window size in legend
• SC-04: Data Range (3/3) - Axes show all data properly with zero=False for better visualization
• SC-05: Legend Accuracy (2/2) - Legend correctly shows "Raw Data" and "7-Day Rolling Average"
• SC-06: Title Format (2/2) - Uses correct format: "line-timeseries-rolling · altair · pyplots.ai"

Data Quality (19/20 pts)

• DQ-01: Feature Coverage (7/8) - Shows seasonal trend well, noise vs smoothed pattern clear; could show more dramatic short-term spikes
• DQ-02: Realistic Context (7/7) - Temperature data with seasonal variation is a perfect realistic scenario
• DQ-03: Appropriate Scale (5/5) - Temperature values from -8°C to 30°C are realistic for a temperate climate winter-to-summer transition

Code Quality (10/10 pts)

• CQ-01: KISS Structure (3/3) - Simple imports → data → plot → save structure, no functions/classes
• 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 API
• CQ-05: Output Correct (1/1) - Saves as plot.png with scale_factor=3.0

Library Features (5/5 pts)

• LF-01: Uses distinctive library features (5/5) - Excellent use of Altair's declarative grammar: alt.condition for conditional styling, pd.melt for tidy data format, proper encoding types (:T, :Q, :N), configure_axis for styling

Strengths

• Excellent use of Altair's declarative grammar with conditional encoding for strokeWidth and opacity
• Clean data transformation using pd.melt for tidy/long format suitable for Altair
• Well-chosen color scheme (#306998 blue, #FFD43B yellow) that is colorblind-safe
• Realistic temperature data scenario with clear seasonal trend
• Proper use of centered rolling window (center=True) for accurate moving average alignment

Weaknesses

• Legend placement overlaps slightly with data points in the upper-right corner; could use orient="bottom" or place outside the plot area

Verdict: APPROVED