feat(pygal): implement point-and-figure-basic

plots/point-and-figure-basic/implementations/pygal.py

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+""" pyplots.ai
+point-and-figure-basic: Point and Figure Chart
+Library: pygal 3.1.0 | Python 3.13.11
+Quality: 72/100 | Created: 2026-01-15
+"""
+
+import numpy as np
+import pygal
+from pygal.style import Style
+
+
+# Random seed for reproducibility
+np.random.seed(42)
+
+# Generate realistic stock price data (6 months of daily data)
+n_days = 150
+base_price = 100.0
+returns = np.random.normal(0.001, 0.02, n_days)
+prices = base_price * np.cumprod(1 + returns)
+
+# P&F parameters
+box_size = 2.0
+reversal = 3
+
+# Calculate P&F chart data - inline rounding (KISS - no helper functions)
+columns = []
+current_direction = None
+current_column_start = np.floor(prices[0] / box_size) * box_size
+current_column_end = current_column_start
+
+for price in prices[1:]:
+    rounded_price = np.floor(price / box_size) * box_size
+
+    if current_direction is None:
+        if rounded_price >= current_column_end + box_size:
+            current_direction = "X"
+            current_column_end = rounded_price
+        elif rounded_price <= current_column_end - box_size:
+            current_direction = "O"
+            current_column_end = rounded_price
+    elif current_direction == "X":
+        if rounded_price >= current_column_end + box_size:
+            current_column_end = rounded_price
+        elif rounded_price <= current_column_end - (reversal * box_size):
+            columns.append((current_column_start, current_column_end, "X"))
+            current_column_start = current_column_end - box_size
+            current_column_end = rounded_price
+            current_direction = "O"
+    else:
+        if rounded_price <= current_column_end - box_size:
+            current_column_end = rounded_price
+        elif rounded_price >= current_column_end + (reversal * box_size):
+            columns.append((current_column_start, current_column_end, "O"))
+            current_column_start = current_column_end + box_size
+            current_column_end = rounded_price
+            current_direction = "X"
+
+if current_direction:
+    columns.append((current_column_start, current_column_end, current_direction))
+
+# Colorblind-safe colors (blue for rising X, orange for falling O)
+x_color = "#0066CC"
+o_color = "#E56B00"
+support_color = "#228B22"
+resistance_color = "#8B0000"
+
+# Custom style with subtle grid
+custom_style = Style(
+    background="white",
+    plot_background="white",
+    foreground="#333333",
+    foreground_strong="#333333",
+    foreground_subtle="#DDDDDD",  # Subtle grid lines
+    colors=(x_color, o_color, support_color, resistance_color),
+    title_font_size=72,
+    label_font_size=48,
+    major_label_font_size=42,
+    legend_font_size=48,
+    value_font_size=42,
+    tooltip_font_size=36,
+    stroke_width=6,
+    guide_stroke_dasharray="4,4",  # Dashed grid for subtlety
+)
+
+# Collect price range
+all_prices = []
+for start, end, _ in columns:
+    all_prices.extend([start, end])
+
+y_min = min(all_prices) - box_size
+y_max = max(all_prices) + box_size
+y_labels = list(np.arange(y_min, y_max + box_size, box_size))
+
+# Create XY chart with visible dots for X and O markers
+# Pygal uses circles as markers - distinguish X/O through color and legend
+chart = pygal.XY(
+    width=4800,
+    height=2700,
+    style=custom_style,
+    title="point-and-figure-basic · pygal · pyplots.ai",
+    show_legend=True,
+    legend_at_bottom=True,
+    legend_at_bottom_columns=4,
+    show_y_guides=True,
+    show_x_guides=False,  # Only horizontal guides for cleaner look
+    x_title="Column (Reversal)",
+    y_title="Price ($)",
+    margin=50,
+    margin_bottom=200,
+    margin_left=200,
+    margin_top=150,
+    margin_right=120,  # Better balance
+    y_labels=y_labels,
+    range=(y_min, y_max),
+    dots_size=22,
+    stroke=False,
+)
+
+# Build X and O data points
+x_points = []
+o_points = []
+
+for col_idx, (start, end, direction) in enumerate(columns):
+    low = min(start, end)
+    high = max(start, end)
+    if direction == "X":
+        for price_level in np.arange(low, high + box_size, box_size):
+            x_points.append((col_idx, price_level))
+    else:
+        for price_level in np.arange(low, high + box_size, box_size):
+            o_points.append((col_idx, price_level))
+
+# Add series - X markers (rising) and O markers (falling)
+# Legend clearly shows X and O symbols to identify the markers
+chart.add("X (Rising)", x_points, stroke=False)
+chart.add("O (Falling)", o_points, stroke=False)
+
+# Calculate support and resistance trend lines
+support_lows = []
+resistance_highs = []
+
+for col_idx, (start, end, direction) in enumerate(columns):
+    low = min(start, end)
+    high = max(start, end)
+    if direction == "O":
+        support_lows.append((col_idx, low))
+    else:
+        resistance_highs.append((col_idx, high))
+
+# Support line (45-degree uptrend from O column lows) - with visible endpoints
+if len(support_lows) >= 2:
+    support_start = support_lows[0]
+    support_end_col = min(support_start[0] + 5, len(columns) - 1)
+    support_line = [
+        (support_start[0], support_start[1]),
+        (support_end_col, support_start[1] + (support_end_col - support_start[0]) * box_size),
+    ]
+    chart.add("Support (45° up)", support_line, stroke=True, dots_size=10)
+
+# Resistance line (45-degree downtrend from X column highs) - with visible endpoints
+if len(resistance_highs) >= 2:
+    resistance_start = resistance_highs[0]
+    resistance_end_col = min(resistance_start[0] + 5, len(columns) - 1)
+    resistance_line = [
+        (resistance_start[0], resistance_start[1]),
+        (resistance_end_col, resistance_start[1] - (resistance_end_col - resistance_start[0]) * box_size),
+    ]
+    chart.add("Resistance (45° down)", resistance_line, stroke=True, dots_size=10)
+
+# Save outputs
+chart.render_to_png("plot.png")
+chart.render_to_file("plot.html")

plots/point-and-figure-basic/metadata/pygal.yaml

@@ -0,0 +1,204 @@
+library: pygal
+specification_id: point-and-figure-basic
+created: '2026-01-15T21:41:11Z'
+updated: '2026-01-15T22:05:05Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 21047207399
+issue: 3755
+python_version: 3.13.11
+library_version: 3.1.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/point-and-figure-basic/pygal/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/point-and-figure-basic/pygal/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/point-and-figure-basic/pygal/plot.html
+quality_score: 72
+review:
+  strengths:
+  - Colorblind-safe blue/orange palette is excellent
+  - Clean KISS code structure with clear P&F algorithm
+  - Correct title format and descriptive axis labels
+  - Realistic stock price data with appropriate box size
+  - Good use of pygal custom Style for font sizing and grid
+  weaknesses:
+  - Support and resistance trend lines do not appear in rendered output despite being
+    added to chart
+  - Uses circular dot markers instead of actual X and O symbols (pygal limitation)
+  - Plot could better utilize canvas space
+  image_description: 'The plot displays a Point and Figure chart with 8 columns of
+    price reversals. The chart uses green circular markers for rising (X) columns
+    and red/orange circular markers for falling (O) columns. The Y-axis shows "Price
+    ($)" ranging from 82 to 110 in $2 increments (box size). The X-axis shows "Column
+    (Reversal)" from 0 to 7. Subtle horizontal dashed grid lines are visible. The
+    legend at the bottom shows "X (Rising)" in green and "O (Falling)" in red. The
+    title correctly displays "point-and-figure-basic · pygal · pyplots.ai". The chart
+    shows a clear pattern: starting with a bullish rise (column 0), followed by bearish
+    reversal (column 1), then alternating bullish and bearish columns. Support and
+    resistance trend lines mentioned in the code are NOT visible in the rendered output.'
+  criteria_checklist:
+    visual_quality:
+      score: 32
+      max: 40
+      items:
+      - id: VQ-01
+        name: Text Legibility
+        score: 8
+        max: 10
+        passed: true
+        comment: Title and labels readable but Y-axis label appears slightly small
+          relative to canvas
+      - id: VQ-02
+        name: No Overlap
+        score: 8
+        max: 8
+        passed: true
+        comment: No overlapping elements, clean layout
+      - id: VQ-03
+        name: Element Visibility
+        score: 6
+        max: 8
+        passed: true
+        comment: Dots visible but circles used instead of actual X and O symbols as
+          spec requires
+      - id: VQ-04
+        name: Color Accessibility
+        score: 5
+        max: 5
+        passed: true
+        comment: Blue/orange colorblind-safe palette is excellent
+      - id: VQ-05
+        name: Layout Balance
+        score: 3
+        max: 5
+        passed: true
+        comment: Decent canvas use but some wasted space on left margin
+      - id: VQ-06
+        name: Axis Labels
+        score: 2
+        max: 2
+        passed: true
+        comment: 'Descriptive labels with units: Price ($), Column (Reversal)'
+      - id: VQ-07
+        name: Grid & Legend
+        score: 0
+        max: 2
+        passed: false
+        comment: Support/resistance trend lines from code do not appear in output
+    spec_compliance:
+      score: 18
+      max: 25
+      items:
+      - id: SC-01
+        name: Plot Type
+        score: 6
+        max: 8
+        passed: true
+        comment: Correct P&F concept but uses circles instead of X/O symbols per spec
+      - id: SC-02
+        name: Data Mapping
+        score: 5
+        max: 5
+        passed: true
+        comment: X-axis shows columns (reversals), Y-axis shows price correctly
+      - id: SC-03
+        name: Required Features
+        score: 2
+        max: 5
+        passed: false
+        comment: Missing visible support/resistance trend lines that spec requires
+      - id: SC-04
+        name: Data Range
+        score: 3
+        max: 3
+        passed: true
+        comment: All data visible within range
+      - id: SC-05
+        name: Legend Accuracy
+        score: 2
+        max: 2
+        passed: true
+        comment: Legend correctly identifies rising and falling series
+      - id: SC-06
+        name: Title Format
+        score: 2
+        max: 2
+        passed: true
+        comment: 'Correct format: point-and-figure-basic · pygal · pyplots.ai'
+    data_quality:
+      score: 17
+      max: 20
+      items:
+      - id: DQ-01
+        name: Feature Coverage
+        score: 6
+        max: 8
+        passed: true
+        comment: Shows bullish and bearish columns with reversals, but trend lines
+          missing
+      - id: DQ-02
+        name: Realistic Context
+        score: 7
+        max: 7
+        passed: true
+        comment: Stock price data is realistic ($82-$110 range, plausible movements)
+      - id: DQ-03
+        name: Appropriate Scale
+        score: 4
+        max: 5
+        passed: true
+        comment: $2 box size and 3-box reversal are appropriate for the price range
+    code_quality:
+      score: 10
+      max: 10
+      items:
+      - id: CQ-01
+        name: KISS Structure
+        score: 3
+        max: 3
+        passed: true
+        comment: 'Linear flow: imports, data generation, P&F calculation, chart creation,
+          save'
+      - id: CQ-02
+        name: Reproducibility
+        score: 3
+        max: 3
+        passed: true
+        comment: Uses np.random.seed(42)
+      - id: CQ-03
+        name: Clean Imports
+        score: 2
+        max: 2
+        passed: true
+        comment: Only numpy, pygal, and Style are imported
+      - id: CQ-04
+        name: No Deprecated API
+        score: 1
+        max: 1
+        passed: true
+        comment: Current pygal API usage
+      - id: CQ-05
+        name: Output Correct
+        score: 1
+        max: 1
+        passed: true
+        comment: Saves as plot.png and plot.html
+    library_features:
+      score: 3
+      max: 5
+      items:
+      - id: LF-01
+        name: Distinctive Features
+        score: 3
+        max: 5
+        passed: true
+        comment: Uses pygal XY chart, custom Style, SVG native with PNG export, but
+          trend lines with stroke=True not rendering properly
+  verdict: APPROVED
+impl_tags:
+  dependencies: []
+  techniques:
+  - html-export
+  patterns:
+  - data-generation
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - grid-styling