feat(bokeh): implement line-retention-cohort

Author: github-actions[bot]

plots/line-retention-cohort/implementations/bokeh.py

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+"""pyplots.ai
+line-retention-cohort: User Retention Curve by Cohort
+Library: bokeh | Python 3.13
+Quality: pending | Created: 2026-03-16
+"""
+
+import numpy as np
+from bokeh.io import export_png, output_file, save
+from bokeh.models import ColumnDataSource, Legend, Span
+from bokeh.plotting import figure
+
+
+# Data
+np.random.seed(42)
+weeks = np.arange(0, 13)
+
+cohorts = {
+    "Jan 2025": {"size": 1245, "decay": 0.18},
+    "Feb 2025": {"size": 1380, "decay": 0.16},
+    "Mar 2025": {"size": 1520, "decay": 0.14},
+    "Apr 2025": {"size": 1410, "decay": 0.12},
+    "May 2025": {"size": 1680, "decay": 0.10},
+}
+
+retention_data = {}
+for cohort, params in cohorts.items():
+    base = 100 * np.exp(-params["decay"] * weeks)
+    noise = np.random.normal(0, 1.5, len(weeks))
+    retention = np.clip(base + noise, 0, 100)
+    retention[0] = 100.0
+    retention_data[cohort] = retention
+
+# Plot
+colors = ["#8FAFC1", "#7B9DB7", "#5A8BA8", "#306998", "#1A4D6E"]
+line_widths = [3, 3.5, 4, 4.5, 5]
+alphas = [0.55, 0.65, 0.75, 0.85, 1.0]
+
+p = figure(
+    width=4800,
+    height=2700,
+    title="line-retention-cohort · bokeh · pyplots.ai",
+    x_axis_label="Weeks Since Signup",
+    y_axis_label="Retention Rate (%)",
+)
+
+legend_items = []
+for i, (cohort, params) in enumerate(cohorts.items()):
+    source = ColumnDataSource(data={"week": weeks, "retention": retention_data[cohort]})
+    label = f"{cohort} (n={params['size']:,})"
+
+    line = p.line(
+        x="week", y="retention", source=source, line_width=line_widths[i], line_color=colors[i], line_alpha=alphas[i]
+    )
+    scatter = p.scatter(
+        x="week",
+        y="retention",
+        source=source,
+        size=12 + i * 2,
+        fill_color=colors[i],
+        fill_alpha=alphas[i],
+        line_color="white",
+        line_width=2,
+    )
+    legend_items.append((label, [line, scatter]))
+
+# Reference line at 20% retention threshold
+threshold = Span(location=20, dimension="width", line_color="#999999", line_dash="dashed", line_width=2, line_alpha=0.7)
+p.add_layout(threshold)
+
+# Legend
+legend = Legend(items=legend_items, location="top_right")
+legend.label_text_font_size = "20pt"
+legend.glyph_height = 30
+legend.glyph_width = 30
+legend.spacing = 12
+legend.padding = 20
+legend.background_fill_alpha = 0.8
+legend.border_line_alpha = 0.3
+p.add_layout(legend)
+
+# Style
+p.title.text_font_size = "42pt"
+p.xaxis.axis_label_text_font_size = "32pt"
+p.yaxis.axis_label_text_font_size = "32pt"
+p.xaxis.major_label_text_font_size = "24pt"
+p.yaxis.major_label_text_font_size = "24pt"
+
+p.y_range.start = 0
+p.y_range.end = 105
+p.x_range.start = -0.3
+p.x_range.end = 12.3
+
+p.ygrid.grid_line_alpha = 0.2
+p.ygrid.grid_line_dash = "dashed"
+p.xgrid.grid_line_alpha = 0
+
+p.background_fill_color = "#fafafa"
+p.border_fill_color = "white"
+
+p.axis.axis_line_width = 2
+p.axis.axis_line_color = "#333333"
+p.axis.major_tick_line_width = 2
+p.axis.minor_tick_line_width = 0
+
+p.toolbar_location = None
+
+# Save
+export_png(p, filename="plot.png")
+
+output_file("plot.html")
+save(p)