Datasets:

andreacenzato
/

Ground-Wing

"""Dataset description figures.

Generates the descriptive figures of the dataset section and of Appendices C, D and E:
parameter distributions with the sensitivity function, the $C_d$/$C_l$ envelope, the mesh base
size study, the ride height sweep behind the choking assessment, the old-vs-new sensitivity
comparison, and the geometric-parameter interaction heatmap.

Run entries are read from the split files in dataset_composition/:

- split_stratified.yaml: the main benchmark split (690 entries, 174 geometries,
  profiles P = 1-12), used for the parameter distributions.
- split_interpolated.yaml: same train/validation, with its test set replaced by the 80
  interpolated-profile entries (20 geometries, profiles P = 13-27). Together with the above
  this gives the 770 simulations of the full dataset, used for the $C_d$/$C_l$ envelope.

Geometry parameters and coefficients for each entry come from run_db.csv

Outputs, under outputs/dataset/:

    parameter_distributions.svg      base_size_cl_conv.svg    base_size_cd_conv.svg
    cd_cl_scatter_all.svg            base_size_cl_err.svg     base_size_cd_err.svg
    ride_height_sweep.svg            interaction_heatmap.svg
    new_sensitivity_comparison.svg   new_sensitivity_comparison.csv
"""

from __future__ import annotations

from itertools import combinations
from pathlib import Path

import matplotlib as mpl
import matplotlib.pyplot as plt
import numpy as np
import pandas as pd
import yaml
from scipy import interpolate
from scipy.interpolate import interp1d
from scipy.stats import gaussian_kde
from sklearn.linear_model import LinearRegression
from sklearn.preprocessing import PolynomialFeatures

here = Path(__file__).resolve().parent
data_dir = here.parents[1] / "dataset_composition"
output_dir = here / "outputs" / "dataset"
output_dir.mkdir(parents=True, exist_ok=True)

# All text is typeset by LaTeX with the same fonts as the paper, and
# every figure is drawn at the width at which it is included.
text_width_in = 6.5
mpl.rcParams.update({
    "text.usetex": True,
    "text.latex.preamble": r"\usepackage{newtxtext,newtxmath}",
    "font.family": "serif",
    "font.size": 9,
    "axes.labelsize": 9,
    "axes.titlesize": 9,
    "legend.fontsize": 8,
    "xtick.labelsize": 8,
    "ytick.labelsize": 8,
})

color_dist = "tab:blue"  # sample distribution: bars and KDE fills
color_sens = "tab:red"  # sensitivity function
color_sens_new = "tab:green"  # sensitivity function of the profile-12 sweep

param_cols = ["P", "CA", "OA", "CS", "OS", "AF"]
param_labels = {
    "P": "Profile, $P$",
    "CA": r"Centerline AoA, $\alpha_c$ [°]",
    "OA": r"Tip Twist, $\theta_t$ [°]",
    "CS": "Centerline Chord, $c_c$ [mm]",
    "OS": "Tip Chord, $c_t$ [mm]",
    "AF": r"Sweep Angle, $\Lambda$ [°]",
}
param_symbols = {
    "P": "$P$", "CA": r"$\alpha_c$", "OA": r"$\theta_t$",
    "CS": "$c_c$", "OS": "$c_t$", "AF": r"$\Lambda$",
}
param_bounds = {
    "CA": (-10.0, 5.0),
    "OA": (-10.0, 10.0),
    "CS": (550.0, 700.0),
    "OS": (350.0, 700.0),
    "AF": (-8.5, 20.0),
}

sens_params = ["CA", "OA", "CS", "OS", "AF"]

split_file = data_dir / "split_stratified.yaml"
interpolated_split_file = data_dir / "split_interpolated.yaml"
run_db_file = data_dir / "run_db.csv"

split_order = ["train", "validation", "test"]


# ---------------------------------------------------------------------------
# Dataset entries: split files joined against the run database
# ---------------------------------------------------------------------------
def read_split(path: Path) -> dict[str, list[str]]:
    """Subset name -> run IDs, from one split file, in split_order."""
    with path.open() as fh:
        sections = yaml.safe_load(fh)
    return {name: [str(run) for run in sections[name]] for name in split_order}


def load_run_db(path: Path) -> pd.DataFrame:
    """The run database, with Cd/Cl derived from the integral force coefficients."""
    db = pd.read_csv(path, sep=";", dtype={"Run #": str})
    db["Cd"] = db["SCx"]
    db["Cl"] = -db["SCz"]
    return db


db = load_run_db(run_db_file)

splits = read_split(split_file)
primary_ids = {entry for ids in splits.values() for entry in ids}
interpolated_ids = sorted(
    {entry for ids in read_split(interpolated_split_file).values() for entry in ids}
    - primary_ids
)

entries = [(entry, name, "primary") for name, ids in splits.items() for entry in ids]
entries += [(entry, "test", "interpolated") for entry in interpolated_ids]

lookup = {
    (row["Run #"], int(row["FRH"]), int(row["RRH"])): row
    for _, row in db.iterrows()
}

records, unmatched = [], []
for entry, split_name, sampling in entries:
    run_no, rh = entry.split("_")
    frh, rrh = int(rh[:2]), int(rh[2:])
    info = lookup.get((run_no, frh, rrh))
    if info is None:
        unmatched.append(entry)
        continue
    rec = {col: float(info[col]) for col in param_cols}
    rec.update(run_id=entry, split=split_name, sampling=sampling, frh=frh, rrh=rrh,
               Cd=info["Cd"], Cl=info["Cl"])
    records.append(rec)

df = pd.DataFrame(records)
df_primary = df[df["sampling"] == "primary"]
print(f"Matched {len(df)} / {len(entries)} run entries ({len(unmatched)} unmatched)")
print(f"  primary sampling: {len(df_primary)} entries, "
      f"{df_primary['run_id'].str.split('_').str[0].nunique()} geometries, "
      f"profiles {int(df_primary['P'].min())}-{int(df_primary['P'].max())}")
print(f"  interpolated: {(df['sampling'] == 'interpolated').sum()} entries, "
      f"profiles {int(df[df['sampling'] == 'interpolated']['P'].min())}-"
      f"{int(df[df['sampling'] == 'interpolated']['P'].max())}")


# ---------------------------------------------------------------------------
# Sensitivity function S(p) = |dCl/dp| + |dCd/dp|
# ---------------------------------------------------------------------------
# CFD sweeps around the baseline geometry CA0 OA0 CS600 OS455 AF10, as
# (parameter values, Cl, Cd). Taken from the `Sensitivity Analysis - <parameter>` rows of
# run_db.csv (SCzav and SCxav): CA runs 0090-0098, OA runs 0099-0106 and 0129-0131, CS runs
# 0107-0112, OS runs 0113-0119, AF runs 0120-0127, with run 0128 the CA = 0 baseline shared by
# the CS and OS sweeps. The sweep was run on the proprietary profile 0, whose geometry is
# not distributed with the dataset, so the values are reproduced here directly.
_sens_data = {
    "CA": (
        np.array([-10, -8, -6, -4, -2, 0, 2, 4, 5]),
        np.array([2.71597, 2.59168, 2.38756, 2.11036, 1.79931, 1.46873, 1.13276, 0.79852, 0.63399]),
        np.array([0.19559, 0.16673, 0.13793, 0.11181, 0.08745, 0.06607, 0.04852, 0.03574, 0.03121]),
    ),
    "OA": (
        np.array([-10, -8, -6, -4, -2, 0, 2, 4, 6, 8, 10]),
        np.array([2.11753, 2.00106, 1.87441, 1.74326, 1.60771, 1.46873, 1.32822, 1.18505, 1.03937, 0.88601, 0.72393]),
        np.array([0.12137, 0.10840, 0.09681, 0.08580, 0.07550, 0.06607, 0.05760, 0.05028, 0.04426, 0.04071, 0.04110]),
    ),
    "CS": (
        np.array([550, 575, 600, 625, 650, 675, 700]),
        np.array([1.39120, 1.43109, 1.46873, 1.50281, 1.53579, 1.56641, 1.59557]),
        np.array([0.06179, 0.06395, 0.06607, 0.06806, 0.07008, 0.07200, 0.07392]),
    ),
    "OS": (
        np.array([350, 400, 455, 500, 550, 600, 650, 700]),
        np.array([1.29316, 1.37725, 1.46873, 1.53883, 1.60908, 1.67319, 1.72398, 1.76696]),
        np.array([0.05588, 0.06063, 0.06607, 0.07047, 0.07517, 0.07981, 0.08379, 0.08746]),
    ),
    "AF": (
        np.array([-8.5, -4, 0, 4, 8, 12, 16, 20]),
        np.array([1.31019, 1.35985, 1.39354, 1.42229, 1.45279, 1.48344, 1.50923, 1.53197]),
        np.array([0.05940, 0.06138, 0.06270, 0.06387, 0.06528, 0.06673, 0.06792, 0.06904]),
    ),
}


def _make_sensitivity_func(param_values, lift, drag):
    lift_deriv = interpolate.make_interp_spline(param_values, lift, k=3).derivative()
    drag_deriv = interpolate.make_interp_spline(param_values, drag, k=3).derivative()
    return lambda p: np.abs(lift_deriv(p)) + np.abs(drag_deriv(p))


sens_funcs = {param: _make_sensitivity_func(*data) for param, data in _sens_data.items()}
for param, (values, _, _) in _sens_data.items():
    print(f"{param}: {len(values)} sweep points, range [{values.min()}, {values.max()}]")


# ---------------------------------------------------------------------------
# Parameter distributions with S(p) overlaid
# ---------------------------------------------------------------------------
fig, axes = plt.subplots(2, 3, figsize=(text_width_in, 4.4))
legend_handles, legend_labels = [], []
for ax, col in zip(axes.flat, param_cols):
    if col == "P":
        counts = df_primary[col].astype(int).value_counts().sort_index()
        ax.bar(counts.index, counts.values, color=color_dist, alpha=0.6,
               edgecolor=color_dist, linewidth=1.5)
        ax.set_xticks(counts.index)
        ax.tick_params(axis="x", labelsize=6)
        ax.set_ylabel("Count", color=color_dist)
        ax.tick_params(axis="y", labelcolor=color_dist)
    else:
        lo, hi = param_bounds[col]
        x_vals = np.linspace(lo, hi, 200)
        density_vals = gaussian_kde(df_primary[col])(x_vals)

        ax.fill_between(x_vals, density_vals, alpha=0.6, color=color_dist,
                        label="Sample distribution")
        ax.plot(x_vals, density_vals, color=color_dist, linewidth=1.5)
        ax.set_ylabel("Density", color=color_dist)
        ax.tick_params(axis="y", labelcolor=color_dist)
        ax.set_xlim(lo, hi)

        # S(p) normalized to its maximum over this parameter's range, so the shape is
        # comparable across subplots despite the differing units of p.
        sens_vals = sens_funcs[col](x_vals)
        ax2 = ax.twinx()
        ax2.plot(x_vals, 100.0 * sens_vals / sens_vals.max(), color=color_sens, linewidth=1.5,
                 label="$S(p)$")
        ax2.set_ylim(0, 105)
        ax2.set_ylabel(r"$S(p)$ [\% of max]", color=color_sens)
        ax2.tick_params(axis="y", labelcolor=color_sens)

        if not legend_handles:
            l1, lb1 = ax.get_legend_handles_labels()
            l2, lb2 = ax2.get_legend_handles_labels()
            legend_handles, legend_labels = l1 + l2, lb1 + lb2
    ax.set_xlabel(param_labels[col])
    ax.grid(True, alpha=0.3)

fig.legend(legend_handles, legend_labels, loc="upper center", ncol=2, bbox_to_anchor=(0.5, 1.04),
           frameon=False)
fig.tight_layout()
fig.savefig(output_dir / "parameter_distributions.svg", bbox_inches="tight")
plt.close(fig)


# ---------------------------------------------------------------------------
# Aerodynamic envelope: Cd vs Cl over every simulated sample
# ---------------------------------------------------------------------------
geom_ids = df["run_id"].str.split("_").str[0]
unique_geoms = geom_ids.unique()
prop_colors = plt.rcParams["axes.prop_cycle"].by_key()["color"]
rng = np.random.default_rng(42)
colors = rng.choice(prop_colors, size=len(unique_geoms))
geom_to_color = dict(zip(unique_geoms, colors))
point_colors = geom_ids.map(geom_to_color).tolist()

fig, ax = plt.subplots(figsize=(0.75 * text_width_in, 3.4))
ax.scatter(df["Cd"], df["Cl"], s=12, alpha=0.75, c=point_colors, edgecolor="none")
ax.set_xlabel("$C_d$")
ax.set_ylabel("$C_l$")
ax.grid(True, alpha=0.3)
fig.tight_layout()
fig.savefig(output_dir / "cd_cl_scatter_all.svg", bbox_inches="tight")
plt.close(fig)


# ---------------------------------------------------------------------------
# Ride height sweep (Appendix E)
# ---------------------------------------------------------------------------
# Flat ride height sweep of a development geometry, used to verify that the four dataset ride
# heights lie outside the nonlinear "choking" regime. Source: run_db.csv, the
# `Flat setup sweep` rows (run 0076), flat setups only.

profile_offset_mm = 57.0  # lowest point of the profile above the lower edge of the endplate
sweep_chord_mm = 600.0  # centerline chord of the development geometry
dataset_rh = [30, 45, 60, 75]  # the four ride heights of the dataset

sweep = db[(db["Description"] == "Flat setup sweep") & (db["FRH"] == db["RRH"])]
sweep = sweep.sort_values("FRH")[["FRH", "Cd", "Cl"]].reset_index(drop=True)
sweep = sweep.rename(columns={"FRH": "RH"})
on_grid = sweep["RH"].isin(dataset_rh)

fig, axes = plt.subplots(1, 2, figsize=(text_width_in, 2.9))
for ax, col, label in zip(axes, ["Cl", "Cd"], ["$C_l$", "$C_d$"]):
    ax.axvspan(min(dataset_rh), max(dataset_rh), color=color_dist, alpha=0.10,
               label="Dataset Range")
    ax.plot(sweep["RH"], sweep[col], "-o", color=color_dist, markersize=4, linewidth=1,
            markerfacecolor="white", label="Sweep")
    ax.plot(sweep.loc[on_grid, "RH"], sweep.loc[on_grid, col], "o", color=color_dist,
            markersize=4, linestyle="none", label="Dataset Ride Heights")
    ax.set_xlabel("Ride Height [mm]")
    ax.set_ylabel(label)
    ax.grid(True, alpha=0.3)
    # Secondary axis: clearance of the lowest point of the profile from the ground, over the
    # centerline chord, i.e. the h/c used in the ground-effect literature. A different datum
    # from the ride height on the primary axis, which is taken at the endplate.
    sec = ax.secondary_xaxis(
        "top",
        functions=(lambda h: (h + profile_offset_mm) / sweep_chord_mm,
                   lambda r: r * sweep_chord_mm - profile_offset_mm),
    )
    sec.set_xlabel("Profile Ground Clearance, $h/c_c$")
    sec.set_xticks([0.15, 0.20, 0.25])

handles, labels_list = axes[0].get_legend_handles_labels()
fig.legend(handles, labels_list, loc="upper center", ncol=3, bbox_to_anchor=(0.5, 1.1),
           frameon=True)
fig.tight_layout()
fig.savefig(output_dir / "ride_height_sweep.svg", bbox_inches="tight")
plt.close(fig)

lo, hi = sweep.iloc[0], sweep.iloc[-1]  # lowest and highest ride height
print(f"\n{len(sweep)} flat ride heights: {list(sweep['RH'])}")
print(f"  |Cl|    {abs(hi['Cl']):.4f} -> {abs(lo['Cl']):.4f} "
      f"({abs(lo['Cl']) / abs(hi['Cl']) - 1:+.1%})")
print(f"  Cd      {hi['Cd']:.4f} -> {lo['Cd']:.4f} ({lo['Cd'] / hi['Cd'] - 1:+.1%})")
print(f"  |Cl|/Cd {abs(hi['Cl']) / hi['Cd']:.1f} -> {abs(lo['Cl']) / lo['Cd']:.1f}")
print(f"  h/c_c   {(lo['RH'] + profile_offset_mm) / sweep_chord_mm:.3f} -> "
      f"{(hi['RH'] + profile_offset_mm) / sweep_chord_mm:.3f}")


# ---------------------------------------------------------------------------
# Mesh base size study
# ---------------------------------------------------------------------------
# Coefficient sensitivity to mesh refinement, relative to the 28M-cell configuration used for
# the dataset. Coefficients are the SCxav/SCzav of the `Mesh convergence - <base size>` rows of
# run_db.csv -- runs 0071, 0072, 0069, 0073, 0074 in the array order below.

base_sizes_mm = np.array([1125, 1000, 875, 750, 625])
n_cells = np.array([9978496, 16452008, 28456075, 44988206, 77560011])
n_cells_m = n_cells / 1e6

scx_avg = np.array([0.07826645, 0.07791031, 0.07736745, 0.07753006, 0.07671507])  # Cd
scz_avg = np.array([1.647213, 1.639564, 1.645484, 1.653249, 1.629673])  # Cl

baseline_idx = 2  # the 28M-cell configuration (875 mm base size)
scx_error = (scx_avg - scx_avg[baseline_idx]) / scx_avg[baseline_idx] * 100
scz_error = (scz_avg - scz_avg[baseline_idx]) / scz_avg[baseline_idx] * 100

cell_to_base = interp1d(n_cells_m, base_sizes_mm, fill_value="extrapolate")
base_to_cell = interp1d(base_sizes_mm, n_cells_m, fill_value="extrapolate")

color_blue_line = "#1f77b4"
color_blue_marker = "#08519c"
color_red_line = "#d62728"
color_red_marker = "#a50f15"

plot_specs = [
    ("base_size_cl_conv.svg", scz_avg, False, r"$C_l$", (1.62, 1.66)),
    ("base_size_cl_err.svg", scz_error, True, r"$\Delta C_l \: [\%]$", (-1.5, 1.5)),
    ("base_size_cd_conv.svg", scx_avg, False, r"$C_d$", (0.075, 0.080)),
    ("base_size_cd_err.svg", scx_error, True, r"$\Delta C_d \: [\%]$", (-1.5, 1.5)),
]

for filename, y_vals, is_error, y_label, y_lims in plot_specs:
    fig, ax = plt.subplots(figsize=(0.48 * text_width_in, 2.5))
    if is_error:
        line_col, marker_col = color_red_line, color_red_marker
        ax.axhspan(-1, 1, color=color_red_line, alpha=0.10)
    else:
        line_col, marker_col = color_blue_line, color_blue_marker

    ax.plot(n_cells_m, y_vals, "-o", color=line_col, markersize=4, linewidth=1,
            markerfacecolor="white", markeredgecolor=marker_col, markeredgewidth=1)
    ax.plot(n_cells_m[baseline_idx], y_vals[baseline_idx], "o", color=marker_col,
            markersize=5, linestyle="none")
    ax.set_xlabel(r"Number of Cells [$\times 10^6$]")
    ax.set_ylabel(y_label)
    ax.set_ylim(*y_lims)
    ax.grid(True, alpha=0.3)

    sec = ax.secondary_xaxis("top", functions=(cell_to_base, base_to_cell))
    sec.set_xlabel("Mesh Base Size [mm]")
    sec.set_xticks([625, 875, 1125])

    fig.tight_layout()
    fig.savefig(output_dir / filename, bbox_inches="tight")
    plt.close(fig)

print("\nMesh independence relative to the 28M-cell configuration (875 mm base size):")
print(f"  77.6M cells (625 mm): Cl error = {scz_error[-1]:+.2f}%, "
      f"Cd error = {scx_error[-1]:+.2f}%")


# ---------------------------------------------------------------------------
# Appendix C: profile-12 sensitivity sweep against the original profile-0 sweep
# ---------------------------------------------------------------------------
# The sensitivity functions above were built on profile 0, a proprietary internal design that
# is not part of the distributed dataset. This section validates them against an equivalent
# sweep on profile 12 (s1223), at the identical baseline and ride height: the `New Sensitivity` 
# rows of run_db.csv. Run 0398 is the baseline and run 0399 is the AF = 0 point of that sweep.

new_sweep = db[db["Description"] == "New Sensitivity"].copy()
new_sweep = new_sweep.sort_values("Run #").reset_index(drop=True)

baseline_vals = {"CA": 0.0, "OA": 0.0, "CS": 600.0, "OS": 455.0, "AF": 10.0}
is_baseline = np.all([new_sweep[p] == v for p, v in baseline_vals.items()], axis=0)
assert is_baseline.sum() == 1, f"expected exactly one baseline run, found {is_baseline.sum()}"
baseline_row = new_sweep[is_baseline].iloc[0]

print(f"\nNew sweep: {len(new_sweep)} runs, profile P={int(baseline_row['P'])}, "
      f"ride height {int(baseline_row['FRH'])}/{int(baseline_row['RRH'])} mm")
print(f"  baseline Cd={baseline_row['Cd']:.5f}, Cl={baseline_row['Cl']:.5f} "
      f"(run {baseline_row['Run #']})")
for param in sens_params:
    other = [p for p in sens_params if p != param]
    mask = np.all([new_sweep[p] == baseline_vals[p] for p in other], axis=0)
    swept = new_sweep[mask]
    print(f"  {param}: {mask.sum()} points (incl. baseline), "
          f"range [{swept[param].min()}, {swept[param].max()}]")


def finite_diff_derivative(x, y):
    """Non-uniform-grid, 2nd-order accurate 3-point derivative estimate at every point.

    Interior points use the symmetric 3-point (Lagrange) formula, which reduces to
    (f(x+h)-f(x-h))/(2h) on a uniform grid; the two endpoints use the matching one-sided
    3-point formula, also 2nd-order accurate.
    """
    n = len(x)
    d = np.empty(n)
    for i in range(1, n - 1):
        h1, h2 = x[i] - x[i - 1], x[i + 1] - x[i]
        d[i] = (-h2 / (h1 * (h1 + h2))) * y[i - 1] + ((h2 - h1) / (h1 * h2)) * y[i] \
            + (h1 / (h2 * (h1 + h2))) * y[i + 1]
    h1, h2 = x[1] - x[0], x[2] - x[1]
    d[0] = (-(2 * h1 + h2) / (h1 * (h1 + h2))) * y[0] + ((h1 + h2) / (h1 * h2)) * y[1] \
        - (h1 / (h2 * (h1 + h2))) * y[2]
    h1, h2 = x[-2] - x[-3], x[-1] - x[-2]
    d[-1] = (h2 / (h1 * (h1 + h2))) * y[-3] - ((h1 + h2) / (h1 * h2)) * y[-2] \
        + ((h1 + 2 * h2) / (h2 * (h1 + h2))) * y[-1]
    return d


# Exact for a quadratic on a non-uniform grid.
_check_x = np.array([0.0, 1.0, 3.0, 4.0, 8.0])
_check_err = np.abs(finite_diff_derivative(_check_x, _check_x**2) - 2 * _check_x).max()
assert _check_err < 1e-12, f"finite_diff_derivative failed the quadratic sanity check ({_check_err})"
print(f"Sanity check passed: max error {_check_err:.2e} on f(x)=x^2")


def central_diff_sens(data):
    values, lift, drag = data
    return values, (np.abs(finite_diff_derivative(values, lift))
                    + np.abs(finite_diff_derivative(values, drag)))


# The new sweep's per-parameter (values, lift, drag) tuples, same structure as _sens_data.
_new_sens_data = {}
for param in sens_params:
    other = [p for p in sens_params if p != param]
    mask = np.all([new_sweep[p] == baseline_vals[p] for p in other], axis=0)
    subset = new_sweep[mask].sort_values(param)
    _new_sens_data[param] = (
        subset[param].to_numpy(), subset["Cl"].to_numpy(), subset["Cd"].to_numpy()
    )

cd_old = {param: central_diff_sens(data) for param, data in _sens_data.items()}
cd_new = {param: central_diff_sens(data) for param, data in _new_sens_data.items()}

# Overlay of the old (profile 0) and new (profile 12) sensitivity functions over each
# parameter's full bound. Both curves share the same units, so no normalization is needed.
fig, axes = plt.subplots(2, 3, figsize=(text_width_in, 4.4))
for ax, col in zip(axes.flat, sens_params):
    lo_b, hi_b = param_bounds[col]
    xo, so = cd_old[col]
    xn, sn = cd_new[col]
    ax.plot(xo, so, "o-", color=color_sens, markersize=4, markerfacecolor="white",
            label="$S(p)$, old (profile 0)")
    ax.plot(xn, sn, "s--", color=color_sens_new, markersize=4, markerfacecolor="white",
            label="$S(p)$, new (profile 12)")
    ax.set_xlabel(param_labels[col])
    ax.set_ylabel("$S(p)$")
    ax.set_xlim(lo_b, hi_b)
    ax.grid(True, alpha=0.3)
axes.flat[-1].axis("off")

handles, labels_list = axes.flat[0].get_legend_handles_labels()
fig.legend(handles, labels_list, loc="upper center", ncol=2, bbox_to_anchor=(0.5, 1.04),
           frameon=False)
fig.tight_layout()
fig.savefig(output_dir / "new_sensitivity_comparison.svg", bbox_inches="tight")
plt.close(fig)

# Each central-difference point set is reconstructed as a piecewise-linear function and
# evaluated on a shared fine grid per parameter, then compared by correlation, relative L2
# difference, and the resulting importance ranking of the five parameters.
rows = []
for param in sens_params:
    lo_b, hi_b = param_bounds[param]
    x_vals = np.linspace(lo_b, hi_b, 500)
    s_old = np.interp(x_vals, *cd_old[param])
    s_new = np.interp(x_vals, *cd_new[param])
    rows.append({
        "param": param,
        "mean_old": s_old.mean(), "mean_new": s_new.mean(),
        "max_old": s_old.max(), "max_new": s_new.max(),
        "correlation": np.corrcoef(s_old, s_new)[0, 1],
        "rel_l2_diff": np.linalg.norm(s_new - s_old) / np.linalg.norm(s_old),
    })
comparison = pd.DataFrame(rows).set_index("param")
comparison["mean_ratio_new_over_old"] = comparison["mean_new"] / comparison["mean_old"]
comparison["rank_old"] = comparison["mean_old"].rank(ascending=False).astype(int)
comparison["rank_new"] = comparison["mean_new"].rank(ascending=False).astype(int)

comparison.to_csv(output_dir / "new_sensitivity_comparison.csv")
print()
print(comparison.round(4).to_string())
print()
print("Importance ranking (1 = most sensitive, by mean S(p) over the parameter's bounds):")
print(f"  old (profile 0):  {list(comparison.sort_values('rank_old').index)}")
print(f"  new (profile 12): {list(comparison.sort_values('rank_new').index)}")


# ---------------------------------------------------------------------------
# Appendix D: geometric parameter interaction
# ---------------------------------------------------------------------------
# Checks the independence assumption behind the sensitivity-weighted sampling (each parameter
# varied one at a time) by fitting a standardized polynomial regression with pairwise
# interaction terms to the full primary-sampled geometry set at the flat 45 mm/45 mm ride
# height.

df_interaction = df_primary[(df_primary["frh"] == 45) & (df_primary["rrh"] == 45)]
print(f"\nInteraction analysis subset: {len(df_interaction)} geometries at 45 mm/45 mm")

X_raw = df_interaction[param_cols].to_numpy(dtype=float)
X_std = (X_raw - X_raw.mean(axis=0)) / X_raw.std(axis=0)

poly = PolynomialFeatures(degree=2, interaction_only=True, include_bias=False)
X_poly = poly.fit_transform(X_std)
pair_indices = list(combinations(range(len(param_cols)), 2))

interaction_matrices = {}
for target in ["Cl", "Cd"]:
    reg = LinearRegression().fit(X_poly, df_interaction[target].to_numpy(dtype=float))
    pair_coefs = reg.coef_[len(param_cols):]
    mat = np.full((len(param_cols), len(param_cols)), np.nan)
    for (i, j), beta in zip(pair_indices, pair_coefs):
        mat[i, j] = mat[j, i] = abs(beta)
    interaction_matrices[target] = mat

param_ticks = [param_symbols[c] for c in param_cols]

fig, axes = plt.subplots(1, 2, figsize=(text_width_in, 3.6))
for ax, target, title in zip(axes, ["Cl", "Cd"], ["$C_l$", "$C_d$"]):
    mat = interaction_matrices[target]
    im = ax.imshow(mat, cmap="viridis")
    ax.set_xticks(range(len(param_cols)))
    ax.set_xticklabels(param_ticks, rotation=45, ha="right")
    ax.set_yticks(range(len(param_cols)))
    ax.set_yticklabels(param_ticks)
    ax.set_title(title)
    vmax = np.nanmax(mat)
    for i in range(len(param_cols)):
        for j in range(len(param_cols)):
            if not np.isnan(mat[i, j]):
                ax.text(j, i, f"{mat[i, j]:.3f}", ha="center", va="center", fontsize=6,
                        color="white" if mat[i, j] < vmax / 2 else "black")
    fig.colorbar(im, ax=ax, fraction=0.046, pad=0.04, label=r"$|\beta_{ij}|$")

fig.tight_layout()
fig.savefig(output_dir / "interaction_heatmap.svg", bbox_inches="tight")
plt.close(fig)

for target in ["Cl", "Cd"]:
    mat = interaction_matrices[target]
    pairs_sorted = sorted(
        ((mat[i, j], param_cols[i], param_cols[j]) for i, j in pair_indices),
        reverse=True,
    )
    print(f"{target}: ranked interactions (top 5 of 15):")
    for val, pi, pj in pairs_sorted[:5]:
        print(f"    {pi}-{pj}: {val:.4f}")

print(f"\nwrote {len(list(output_dir.iterdir()))} files to {output_dir}")