feat(pygal): implement ohlc-bar

[github-actions]

Implementation: ohlc-bar - pygal

Implements the pygal version of ohlc-bar.

File: plots/ohlc-bar/implementations/pygal.py

Parent Issue: #3293

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

The plot displays an OHLC (Open-High-Low-Close) bar chart showing 40 trading days of stock price data. Each bar consists of a vertical line (high-low range) with horizontal tick marks extending left for open price and right for close price. Green bars indicate bullish days (close ≥ open) and red bars indicate bearish days (close < open). The price ranges from approximately $130 to $166, showing an overall downward trend with volatility. The title "ohlc-bar · pygal · pyplots.ai" is displayed at the top. Axes are labeled "Trading Day" (x-axis, numeric 0-36) and "Price ($)" (y-axis). A legend at the bottom shows "Up (Close ≥ Open)" in green and "Down (Close < Open)" in red. Light gray grid lines are visible in the background.

Quality Score: 82/100

Criteria Checklist

Visual Quality (32/40)

• VQ-01: Text Legibility (8/10) - Title and axis labels are readable, font sizes appropriate for canvas
• VQ-02: No Overlap (6/8) - Minor overlap between adjacent OHLC bars due to line-based rendering
• VQ-03: Element Visibility (6/8) - OHLC bars are visible but tick marks could be more prominent
• VQ-04: Color Accessibility (5/5) - Green/red color scheme with sufficient contrast
• VQ-05: Layout Balance (5/5) - Good use of canvas space, balanced margins
• VQ-06: Axis Labels (2/2) - "Price ($)" includes units, "Trading Day" is descriptive
• VQ-07: Grid & Legend (0/2) - Grid is subtle but legend placement at bottom is slightly disconnected

Spec Compliance (21/25)

• SC-01: Plot Type (8/8) - Correct OHLC bar chart type
• SC-02: Data Mapping (5/5) - High-low vertical lines, open/close ticks correctly placed
• SC-03: Required Features (3/5) - Has color differentiation for up/down, but X-axis uses numeric index instead of dates
• SC-04: Data Range (3/3) - All data visible within axes
• SC-05: Legend Accuracy (0/2) - Legend shows series but could be more descriptive
• SC-06: Title Format (2/2) - Correct format: "ohlc-bar · pygal · pyplots.ai"

Data Quality (18/20)

• DQ-01: Feature Coverage (7/8) - Shows both bullish and bearish bars, realistic price movement, overall trend visible
• DQ-02: Realistic Context (7/7) - Stock price data with realistic volatility and price range ($130-$166)
• DQ-03: Appropriate Scale (4/5) - 40 trading days is appropriate, prices realistic for a stock

Code Quality (8/10)

• CQ-01: KISS Structure (3/3) - Clean imports → data → plot → save structure
• CQ-02: Reproducibility (3/3) - np.random.seed(42) set
• CQ-03: Clean Imports (2/2) - All imports used (numpy, pandas, pygal, Style)
• CQ-04: No Deprecated API (0/1) - Uses current API
• CQ-05: Output Correct (0/1) - Saves both plot.png and plot.html correctly

Library Features (3/5)

• LF-01: Uses distinctive library features (3/5) - Uses pygal's XY chart with custom Style, but OHLC visualization is manually constructed rather than using a native chart type

Strengths

• Creative approach to OHLC visualization using pygal's XY chart with line segments
• Proper color differentiation between up (green) and down (red) bars
• Realistic stock price data with good variety of bullish and bearish periods
• Clean code structure following KISS principles
• Appropriate canvas sizing (4800x2700) and font sizes for readability
• Grid lines help read exact price levels as specified

Weaknesses

• X-axis shows numeric trading day index (0-36) instead of actual dates despite generating date_range
• OHLC tick marks (open/close horizontal lines) could be more visually prominent
• Legend labels could better explain what the colors represent
• Grid styling could be more subtle (lower alpha)

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 an OHLC (Open-High-Low-Close) bar chart with 40 trading days of stock price data on a white background. Green bars indicate bullish days (close ≥ open) and red bars indicate bearish days (close < open). Each OHLC bar correctly shows: a vertical line for the high-low range, a left horizontal tick for the opening price, and a right horizontal tick for the closing price. The chart shows a general downtrend from approximately $150 to $130 over the period. The title "ohlc-bar · pygal · pyplots.ai" appears at top center. Y-axis is labeled "Price ($)" ranging from ~130 to ~166. X-axis is labeled "Trading Day" with numeric indices 0-36. A legend at the bottom shows "Up (Close ≥ Open)" in green and "Down (Close < Open)" in red. Light gray dashed vertical grid lines are visible.

Quality Score: 90/100

Criteria Checklist

Visual Quality (35/40)

• VQ-01: Text Legibility (10/10) - Title, axis labels, and tick labels are all clearly readable at the canvas size
• VQ-02: No Overlap (8/8) - No overlapping text elements; bars are well-spaced
• VQ-03: Element Visibility (7/8) - OHLC bars are visible and distinguishable, though some bars overlap slightly due to data density
• VQ-04: Color Accessibility (5/5) - Green/red color scheme is standard for financial charts and has good contrast on white background
• VQ-05: Layout Balance (3/5) - Good use of canvas space, but x-axis shows numeric indices instead of date labels which reduces context
• VQ-06: Axis Labels (2/2) - Y-axis has "Price ($)" with units, X-axis has "Trading Day" which is descriptive
• VQ-07: Grid & Legend (0/2) - Only vertical grid lines visible (no horizontal guides for price levels); legend is well-placed but uses different label format than code

Spec Compliance (23/25)

• SC-01: Plot Type (8/8) - Correct OHLC bar chart with vertical lines and horizontal ticks
• SC-02: Data Mapping (5/5) - Date on X-axis, price on Y-axis, OHLC values correctly mapped
• SC-03: Required Features (4/5) - Has open/close ticks, high-low lines, color coding for up/down; but spec mentions horizontal grid lines for reading price levels which are missing
• SC-04: Data Range (3/3) - All data points visible within axes range
• SC-05: Legend Accuracy (1/2) - Legend labels differ from code (shows "Up/Down" not "Bullish/Bearish")
• SC-06: Title Format (2/2) - Correct format: "ohlc-bar · pygal · pyplots.ai"

Data Quality (19/20)

• DQ-01: Feature Coverage (8/8) - Shows both bullish and bearish bars, various price ranges, realistic price movements
• DQ-02: Realistic Context (6/7) - Plausible stock price scenario with business days, but no specific stock context
• DQ-03: Appropriate Scale (5/5) - Price values ($130-$166) are realistic for stock prices

Code Quality (10/10)

• CQ-01: KISS Structure (3/3) - Clean imports → data → plot → save structure, no unnecessary functions/classes
• CQ-02: Reproducibility (3/3) - Uses np.random.seed(42) for reproducibility
• CQ-03: Clean Imports (2/2) - All imports are used (numpy, pandas, pygal, Style)
• CQ-04: No Deprecated API (1/1) - Uses current pygal API
• CQ-05: Output Correct (1/1) - Saves as plot.png and plot.html

Library Features (3/5)

• LF-01: Uses distinctive library features (3/5) - Uses pygal Style customization and XY chart with line segments to create OHLC bars; creative use of None separators for discontinuous lines

Strengths

• Correct OHLC bar representation using pygal XY chart with creative line segment approach
• Good color differentiation between bullish (green) and bearish (red) bars
• Clean code structure following KISS principles
• Appropriate font sizes for the 4800x2700 canvas
• Realistic stock price data generation with proper OHLC relationships

Weaknesses

• X-axis shows numeric indices instead of actual date labels despite dates being generated
• Missing horizontal grid lines which spec mentions for reading price levels
• Legend labels in output differ from code comments (Up/Down vs Bullish/Bearish)

Verdict: APPROVED