feat(seaborn): implement scatter-lag

Author: github-actions[bot]

plots/scatter-lag/implementations/seaborn.py

@@ -0,0 +1,95 @@
+"""pyplots.ai
+scatter-lag: Lag Plot for Time Series Autocorrelation Diagnosis
+Library: seaborn | Python 3.13
+Quality: pending | Created: 2026-04-12
+"""
+
+import matplotlib.pyplot as plt
+import numpy as np
+import pandas as pd
+import seaborn as sns
+
+
+# Data - synthetic AR(1) process with strong positive autocorrelation
+np.random.seed(42)
+n = 500
+phi = 0.85
+noise = np.random.normal(0, 1, n)
+
+values = np.zeros(n)
+values[0] = noise[0]
+for t in range(1, n):
+    values[t] = phi * values[t - 1] + noise[t]
+
+# Lag plot data (lag = 1)
+lag = 1
+y_t = values[:-lag]
+y_t_lag = values[lag:]
+time_index = np.arange(len(y_t))
+
+df = pd.DataFrame({"y(t)": y_t, "y(t + 1)": y_t_lag, "Time Index": time_index})
+
+r = np.corrcoef(y_t, y_t_lag)[0, 1]
+
+# Plot
+sns.set_theme(
+    style="ticks",
+    context="talk",
+    font_scale=1.1,
+    rc={"font.family": "sans-serif", "axes.edgecolor": "#888888", "axes.linewidth": 0.8},
+)
+
+fig, ax = plt.subplots(figsize=(16, 9))
+
+scatter = ax.scatter(
+    y_t, y_t_lag, c=time_index, cmap="viridis", s=70, alpha=0.65, edgecolors="white", linewidths=0.4, zorder=3
+)
+
+# Diagonal reference line (y = x)
+data_min = min(y_t.min(), y_t_lag.min())
+data_max = max(y_t.max(), y_t_lag.max())
+margin = (data_max - data_min) * 0.05
+ax.plot(
+    [data_min - margin, data_max + margin],
+    [data_min - margin, data_max + margin],
+    color="#c44e52",
+    linewidth=2,
+    linestyle="--",
+    alpha=0.6,
+    zorder=2,
+)
+
+# Colorbar for temporal structure
+cbar = plt.colorbar(scatter, ax=ax, pad=0.02, aspect=30)
+cbar.set_label("Time Index", fontsize=18, color="#444444")
+cbar.ax.tick_params(labelsize=14)
+
+# Correlation coefficient
+ax.annotate(
+    f"r = {r:.2f}",
+    xy=(0.03, 0.96),
+    xycoords="axes fraction",
+    fontsize=18,
+    fontweight="bold",
+    color="#444444",
+    ha="left",
+    va="top",
+    bbox={"boxstyle": "round,pad=0.4", "facecolor": "white", "edgecolor": "#cccccc", "alpha": 0.9},
+)
+
+# Style
+ax.set_title(
+    "AR(1) Autocorrelation · scatter-lag · seaborn · pyplots.ai",
+    fontsize=24,
+    fontweight="medium",
+    color="#333333",
+    pad=16,
+)
+ax.set_xlabel("y(t)", fontsize=20, color="#444444")
+ax.set_ylabel("y(t + 1)", fontsize=20, color="#444444")
+ax.tick_params(axis="both", labelsize=16, colors="#555555")
+ax.grid(True, alpha=0.15, linewidth=0.6)
+sns.despine(ax=ax)
+
+plt.tight_layout()
+plt.savefig("plot.png", dpi=300, bbox_inches="tight")