feat(matplotlib): implement andrews-curves (#6818)

## Implementation: `andrews-curves` - python/matplotlib

Implements the **python/matplotlib** version of `andrews-curves`.

**File:** `plots/andrews-curves/implementations/python/matplotlib.py`

**Parent Issue:** #2859

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/25918654244)*

---------

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

Author: github-actions[bot]

plots/andrews-curves/implementations/python/matplotlib.py

@@ -1,16 +1,27 @@
-""" pyplots.ai
+""" anyplot.ai
 andrews-curves: Andrews Curves for Multivariate Data
-Library: matplotlib 3.10.8 | Python 3.13.11
-Quality: 91/100 | Created: 2025-12-30
+Library: matplotlib 3.10.9 | Python 3.13.13
+Quality: 90/100 | Updated: 2026-05-15
 """
 
+import os
+
 import matplotlib.pyplot as plt
 import numpy as np
 from sklearn.datasets import load_iris
 from sklearn.preprocessing import StandardScaler
 
 
-# Load and prepare data
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+BRAND = "#009E73"
+OKABE_ITO = ["#009E73", "#D55E00", "#0072B2"]
+
+# Data
+np.random.seed(42)
 iris = load_iris()
 X = iris.data
 y = iris.target
@@ -38,31 +49,40 @@
 # Compute all Andrews curves: each row of X_scaled dot basis.T gives one curve
 curves = X_scaled @ basis.T  # shape: (150, 200)
 
-# Create plot
-fig, ax = plt.subplots(figsize=(16, 9))
-
-# Colors for each species (Python Blue, Python Yellow, and a complementary color)
-colors = ["#306998", "#FFD43B", "#E06C75"]
+# Plot
+fig, ax = plt.subplots(figsize=(16, 9), facecolor=PAGE_BG)
+ax.set_facecolor(PAGE_BG)
 
 # Plot Andrews curves for each observation
 for i in range(len(curves)):
-    ax.plot(t, curves[i], color=colors[y[i]], alpha=0.4, linewidth=1.5)
+    ax.plot(t, curves[i], color=OKABE_ITO[y[i]], alpha=0.4, linewidth=2.5)
 
 # Create legend with sample lines
 for idx, species in enumerate(species_names):
-    ax.plot([], [], color=colors[idx], linewidth=3, label=species, alpha=0.8)
+    ax.plot([], [], color=OKABE_ITO[idx], linewidth=3, label=species, alpha=0.4)
+
+# Style
+ax.set_xlabel("t (radians)", fontsize=20, color=INK)
+ax.set_ylabel("f(t)", fontsize=20, color=INK)
+ax.set_title("andrews-curves · matplotlib · anyplot.ai", fontsize=24, fontweight="medium", color=INK)
+ax.tick_params(axis="both", labelsize=16, colors=INK_SOFT)
+ax.spines["top"].set_visible(False)
+ax.spines["right"].set_visible(False)
+for s in ("left", "bottom"):
+    ax.spines[s].set_color(INK_SOFT)
+ax.yaxis.grid(True, alpha=0.15, linewidth=0.8, color=INK)
 
-# Styling
-ax.set_xlabel("t (radians)", fontsize=20)
-ax.set_ylabel("f(t)", fontsize=20)
-ax.set_title("andrews-curves · matplotlib · pyplots.ai", fontsize=24)
-ax.tick_params(axis="both", labelsize=16)
-ax.legend(fontsize=16, loc="upper right")
-ax.grid(True, alpha=0.3, linestyle="--")
+# Legend styling
+leg = ax.legend(fontsize=16, loc="upper right")
+if leg:
+    leg.get_frame().set_facecolor(ELEVATED_BG)
+    leg.get_frame().set_edgecolor(INK_SOFT)
+    leg.get_frame().set_linewidth(0.8)
+    plt.setp(leg.get_texts(), color=INK_SOFT)
 
 # Set x-axis ticks at meaningful positions
 ax.set_xticks([-np.pi, -np.pi / 2, 0, np.pi / 2, np.pi])
 ax.set_xticklabels(["-π", "-π/2", "0", "π/2", "π"], fontsize=16)
 
 plt.tight_layout()
-plt.savefig("plot.png", dpi=300, bbox_inches="tight")
+plt.savefig(f"plot-{THEME}.png", dpi=300, bbox_inches="tight", facecolor=PAGE_BG)