feat(bokeh): implement campbell-basic (#4250)

## Implementation: `campbell-basic` - bokeh

Implements the **bokeh** version of `campbell-basic`.

**File:** `plots/campbell-basic/implementations/bokeh.py`

**Parent Issue:** #4241

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/22043026932)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/campbell-basic/implementations/bokeh.py

@@ -0,0 +1,289 @@
+""" pyplots.ai
+campbell-basic: Campbell Diagram
+Library: bokeh 3.8.2 | Python 3.14.3
+Quality: 95/100 | Created: 2026-02-15
+"""
+
+import numpy as np
+from bokeh.io import export_png, output_file, save
+from bokeh.models import BoxAnnotation, ColumnDataSource, HoverTool, Label, Legend, LegendItem, Range1d, Span
+from bokeh.plotting import figure
+
+
+# Data
+speeds = np.linspace(0, 6000, 100)
+
+# Natural frequency modes (Hz) with pronounced rotordynamic behavior
+mode_1_bending = 25 + 0.008 * speeds + 3.5 * np.sin(speeds / 2800 * np.pi)
+mode_2_bending = 62 - 0.006 * speeds + 2.0 * np.sin(speeds / 2200 * np.pi)
+mode_1_torsional = 85 + 0.005 * speeds
+mode_axial = 110 - 0.004 * speeds + 2.5 * np.cos(speeds / 3200 * np.pi)
+mode_3_bending = 130 + 0.010 * speeds - 4.0 * np.cos(speeds / 2600 * np.pi)
+
+modes = {
+    "1st Bending": mode_1_bending,
+    "2nd Bending": mode_2_bending,
+    "1st Torsional": mode_1_torsional,
+    "Axial": mode_axial,
+    "3rd Bending": mode_3_bending,
+}
+
+# Engine order lines: frequency = order * speed / 60
+engine_orders = [1, 2, 3]
+eo_frequencies = {order: order * speeds / 60 for order in engine_orders}
+
+# Find critical speed intersections via sign-change interpolation
+critical_speeds_rpm = []
+critical_speeds_freq = []
+critical_speed_labels = []
+critical_in_operating = []
+
+for order in engine_orders:
+    eo_freq = eo_frequencies[order]
+    for mode_name, mode_freq in modes.items():
+        diff = eo_freq - mode_freq
+        sign_changes = np.where(np.diff(np.sign(diff)))[0]
+        for idx in sign_changes:
+            denom = abs(diff[idx]) + abs(diff[idx + 1])
+            if denom == 0:
+                continue
+            frac = abs(diff[idx]) / denom
+            rpm_val = speeds[idx] + frac * (speeds[idx + 1] - speeds[idx])
+            freq_val = mode_freq[idx] + frac * (mode_freq[idx + 1] - mode_freq[idx])
+            if 100 < rpm_val < 5900 and 5 < freq_val < 195:
+                critical_speeds_rpm.append(rpm_val)
+                critical_speeds_freq.append(freq_val)
+                critical_speed_labels.append(f"{order}x × {mode_name}")
+                critical_in_operating.append(3000 <= rpm_val <= 5000)
+
+# Compute y-range
+all_freqs = np.concatenate(list(modes.values()))
+y_max_data = max(np.max(all_freqs), max(critical_speeds_freq) if critical_speeds_freq else 0)
+y_max = min(int(np.ceil(y_max_data / 10) * 10) + 15, 200)
+
+# Plot
+p = figure(
+    width=4800,
+    height=2700,
+    title="campbell-basic · bokeh · pyplots.ai",
+    x_axis_label="Rotational Speed (RPM)",
+    y_axis_label="Frequency (Hz)",
+    x_range=Range1d(-100, 6300),
+    y_range=Range1d(0, y_max),
+)
+
+# Operating range shading (3000–5000 RPM)
+operating_zone = BoxAnnotation(
+    left=3000,
+    right=5000,
+    fill_color="#306998",
+    fill_alpha=0.06,
+    line_color="#306998",
+    line_alpha=0.3,
+    line_dash="dotted",
+    line_width=2,
+)
+p.add_layout(operating_zone)
+
+# Operating range boundary lines for crisp delineation
+for rpm_boundary in [3000, 5000]:
+    boundary_line = Span(
+        location=rpm_boundary,
+        dimension="height",
+        line_color="#306998",
+        line_alpha=0.35,
+        line_width=2,
+        line_dash="dashed",
+    )
+    p.add_layout(boundary_line)
+
+# Operating range label
+op_label = Label(
+    x=4000,
+    y=y_max * 0.04,
+    text="Operating Range (3000–5000 RPM)",
+    text_font_size="18pt",
+    text_color="#306998",
+    text_alpha=0.8,
+    text_align="center",
+    text_font_style="bold italic",
+)
+p.add_layout(op_label)
+
+# Danger zone highlighting around critical speeds within operating range
+for rpm_val, freq_val, in_op in zip(critical_speeds_rpm, critical_speeds_freq, critical_in_operating, strict=True):
+    if in_op:
+        danger = BoxAnnotation(
+            left=rpm_val - 120,
+            right=rpm_val + 120,
+            bottom=freq_val - 4,
+            top=freq_val + 4,
+            fill_color="#C44E52",
+            fill_alpha=0.10,
+            line_color="#C44E52",
+            line_alpha=0.25,
+            line_width=1,
+        )
+        p.add_layout(danger)
+
+# Natural frequency mode colors — distinct, colorblind-safe palette
+# Python Blue, amber, rose, violet, teal — all perceptually distinct
+mode_colors = ["#306998", "#E8A838", "#C44E52", "#7A68A6", "#48A9A6"]
+
+# Plot natural frequency curves
+legend_items = []
+for i, (mode_name, mode_freq) in enumerate(modes.items()):
+    source = ColumnDataSource(data={"speed": speeds, "freq": mode_freq})
+    line = p.line(x="speed", y="freq", source=source, line_width=4, line_color=mode_colors[i], line_alpha=0.9)
+    legend_items.append(LegendItem(label=mode_name, renderers=[line]))
+
+# Engine order lines (lighter, thinner to reduce visual clutter)
+eo_color = "#666666"
+
+for order in engine_orders:
+    eo_freq = eo_frequencies[order]
+    mask = eo_freq <= y_max
+    clipped_speeds = speeds[mask]
+    clipped_freq = eo_freq[mask]
+
+    source = ColumnDataSource(data={"speed": clipped_speeds, "freq": clipped_freq})
+    line = p.line(
+        x="speed", y="freq", source=source, line_width=2, line_color=eo_color, line_dash=[12, 8], line_alpha=0.6
+    )
+    legend_items.append(LegendItem(label=f"{order}x EO", renderers=[line]))
+
+# Engine order labels — positioned at right edge, offset to avoid crowding
+for order in engine_orders:
+    freq_at_max = order * 6000 / 60
+    if freq_at_max > y_max - 5:
+        label_rpm = (y_max - 12) * 60 / order
+        label_freq = y_max - 10
+    else:
+        label_rpm = 5850
+        label_freq = freq_at_max
+
+    label = Label(
+        x=label_rpm,
+        y=label_freq,
+        text=f" {order}x",
+        text_font_size="20pt",
+        text_color="#555555",
+        text_font_style="bold",
+        text_baseline="middle",
+    )
+    p.add_layout(label)
+
+# Critical speed markers — dark orange, clearly distinct from crimson mode lines
+if critical_speeds_rpm:
+    crit_source = ColumnDataSource(
+        data={
+            "rpm": critical_speeds_rpm,
+            "freq": critical_speeds_freq,
+            "label": critical_speed_labels,
+            "rpm_display": [f"{r:.0f}" for r in critical_speeds_rpm],
+            "freq_display": [f"{f:.1f}" for f in critical_speeds_freq],
+            "in_operating": ["YES — CAUTION" if op else "No" for op in critical_in_operating],
+        }
+    )
+    crit_scatter = p.scatter(
+        x="rpm",
+        y="freq",
+        source=crit_source,
+        marker="diamond",
+        size=28,
+        fill_color="#E65100",
+        line_color="#FFFFFF",
+        line_width=2.5,
+        fill_alpha=0.9,
+    )
+    legend_items.append(LegendItem(label="Critical Speed", renderers=[crit_scatter]))
+
+    # HoverTool with enriched tooltips (Bokeh distinctive feature)
+    hover = HoverTool(
+        renderers=[crit_scatter],
+        tooltips=[
+            ("Intersection", "@label"),
+            ("RPM", "@rpm_display"),
+            ("Frequency", "@freq_display Hz"),
+            ("In Operating Range?", "@in_operating"),
+        ],
+        mode="mouse",
+    )
+    p.add_tools(hover)
+
+    # Annotate the most critical intersection in the operating range
+    op_crits = [
+        (r, f, lbl)
+        for r, f, lbl, op in zip(
+            critical_speeds_rpm, critical_speeds_freq, critical_speed_labels, critical_in_operating, strict=True
+        )
+        if op
+    ]
+    if op_crits:
+        op_crits.sort(key=lambda x: x[1])
+        worst_rpm, worst_freq, worst_label = op_crits[0]
+        annotation = Label(
+            x=worst_rpm + 280,
+            y=worst_freq + 8,
+            text=f"⚠ {worst_label} @ {worst_rpm:.0f} RPM",
+            text_font_size="15pt",
+            text_color="#E65100",
+            text_font_style="bold",
+            text_alpha=0.85,
+        )
+        p.add_layout(annotation)
+
+# Legend — positioned top-left, compact to minimize data overlap
+legend = Legend(
+    items=legend_items,
+    location="top_left",
+    label_text_font_size="16pt",
+    glyph_width=50,
+    glyph_height=26,
+    spacing=10,
+    padding=16,
+    background_fill_color="#FFFFFF",
+    background_fill_alpha=0.88,
+    border_line_color="#CCCCCC",
+    border_line_alpha=0.25,
+    border_line_width=1,
+)
+p.add_layout(legend)
+
+# Title styling
+p.title.text_font_size = "28pt"
+p.title.align = "center"
+p.title.text_color = "#222222"
+
+# Axis styling
+p.xaxis.axis_label_text_font_size = "22pt"
+p.yaxis.axis_label_text_font_size = "22pt"
+p.xaxis.major_label_text_font_size = "18pt"
+p.yaxis.major_label_text_font_size = "18pt"
+p.xaxis.axis_label_text_color = "#333333"
+p.yaxis.axis_label_text_color = "#333333"
+p.xaxis.major_label_text_color = "#555555"
+p.yaxis.major_label_text_color = "#555555"
+p.xaxis.axis_line_color = "#BBBBBB"
+p.yaxis.axis_line_color = "#BBBBBB"
+p.xaxis.major_tick_line_color = "#BBBBBB"
+p.yaxis.major_tick_line_color = "#BBBBBB"
+p.xaxis.minor_tick_line_color = None
+p.yaxis.minor_tick_line_color = None
+
+# Grid styling (subtle, refined)
+p.xgrid.grid_line_color = "#E0E0E0"
+p.xgrid.grid_line_alpha = 0.4
+p.ygrid.grid_line_color = "#E0E0E0"
+p.ygrid.grid_line_alpha = 0.4
+
+# Background and frame
+p.background_fill_color = "#FAFAFA"
+p.border_fill_color = "#FFFFFF"
+p.outline_line_color = None
+
+# Save
+export_png(p, filename="plot.png")
+
+output_file("plot.html")
+save(p)