name: ML Model Explanation description: Interpret machine learning models using SHAP, LIME, feature importance, partial dependence, and attention visualization for explainability

ML Model Explanation

Model explainability makes machine learning decisions transparent and interpretable, enabling trust, compliance, debugging, and actionable insights from predictions.

Explanation Techniques

• Feature Importance: Global feature contribution to predictions
• SHAP Values: Game theory-based feature attribution
• LIME: Local linear approximations for individual predictions
• Partial Dependence Plots: Feature relationship with predictions
• Attention Maps: Visualization of model focus areas
• Surrogate Models: Simpler interpretable approximations

Explainability Types

• Global: Overall model behavior and patterns
• Local: Explanation for individual predictions
• Feature-Level: Which features matter most
• Model-Level: How different components interact

Python Implementation

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
from sklearn.datasets import make_classification
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import StandardScaler
from sklearn.ensemble import RandomForestClassifier, GradientBoostingClassifier
from sklearn.linear_model import LogisticRegression
from sklearn.tree import DecisionTreeClassifier, plot_tree
from sklearn.inspection import partial_dependence, permutation_importance
import warnings
warnings.filterwarnings('ignore')

print("=== 1. Feature Importance Analysis ===")

# Create dataset
X, y = make_classification(n_samples=1000, n_features=20, n_informative=10,
                          n_redundant=5, random_state=42)
feature_names = [f'Feature_{i}' for i in range(20)]
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)

# Train models
rf_model = RandomForestClassifier(n_estimators=100, random_state=42)
rf_model.fit(X_train, y_train)

gb_model = GradientBoostingClassifier(n_estimators=100, random_state=42)
gb_model.fit(X_train, y_train)

# Feature importance methods
print("\n=== Feature Importance Comparison ===")

# 1. Impurity-based importance (default)
impurity_importance = rf_model.feature_importances_

# 2. Permutation importance
perm_importance = permutation_importance(rf_model, X_test, y_test, n_repeats=10, random_state=42)

# Create comparison dataframe
importance_df = pd.DataFrame({
    'Feature': feature_names,
    'Impurity': impurity_importance,
    'Permutation': perm_importance.importances_mean
}).sort_values('Impurity', ascending=False)

print("\nTop 10 Most Important Features (by Impurity):")
print(importance_df.head(10)[['Feature', 'Impurity']])

# 2. SHAP-like Feature Attribution
print("\n=== SHAP-like Feature Attribution ===")

class SimpleShapCalculator:
    def __init__(self, model, X_background):
        self.model = model
        self.X_background = X_background
        self.baseline = model.predict_proba(X_background.mean(axis=0).reshape(1, -1))[0]

    def predict_difference(self, X_sample):
        """Get prediction difference from baseline"""
        pred = self.model.predict_proba(X_sample)[0]
        return pred - self.baseline

    def calculate_shap_values(self, X_instance, n_iterations=100):
        """Approximate SHAP values"""
        shap_values = np.zeros(X_instance.shape[1])
        n_features = X_instance.shape[1]

        for i in range(n_iterations):
            # Random feature subset
            subset_mask = np.random.random(n_features) > 0.5

            # With and without feature
            X_with = X_instance.copy()
            X_without = X_instance.copy()
            X_without[0, ~subset_mask] = self.X_background[0, ~subset_mask]

            # Marginal contribution
            contribution = (self.predict_difference(X_with)[1] -
                          self.predict_difference(X_without)[1])

            shap_values[~subset_mask] += contribution / n_iterations

        return shap_values

shap_calc = SimpleShapCalculator(rf_model, X_train)

# Calculate SHAP values for a sample
sample_idx = 0
shap_vals = shap_calc.calculate_shap_values(X_test[sample_idx:sample_idx+1], n_iterations=50)

print(f"\nSHAP Values for Sample {sample_idx}:")
shap_df = pd.DataFrame({
    'Feature': feature_names,
    'SHAP_Value': shap_vals
}).sort_values('SHAP_Value', key=abs, ascending=False)

print(shap_df.head(10)[['Feature', 'SHAP_Value']])

# 3. Partial Dependence Analysis
print("\n=== 3. Partial Dependence Analysis ===")

# Calculate partial dependence for top features
top_features = importance_df['Feature'].head(3).values
top_feature_indices = [feature_names.index(f) for f in top_features]

pd_data = {}
for feature_idx in top_feature_indices:
    pd_result = partial_dependence(rf_model, X_test, [feature_idx])
    pd_data[feature_names[feature_idx]] = pd_result

print(f"Partial dependence calculated for features: {list(pd_data.keys())}")

# 4. LIME - Local Interpretable Model-agnostic Explanations
print("\n=== 4. LIME (Local Surrogate Model) ===")

class SimpleLIME:
    def __init__(self, model, X_train):
        self.model = model
        self.X_train = X_train
        self.scaler = StandardScaler()
        self.scaler.fit(X_train)

    def explain_instance(self, instance, n_samples=1000, n_features=10):
        """Explain prediction using local linear model"""
        # Generate perturbed samples
        scaled_instance = self.scaler.transform(instance.reshape(1, -1))
        perturbations = np.random.normal(scaled_instance, 0.3, (n_samples, instance.shape[0]))

        # Get predictions
        predictions = self.model.predict_proba(perturbations)[:, 1]

        # Train local linear model
        distances = np.sum((perturbations - scaled_instance) ** 2, axis=1)
        weights = np.exp(-distances)

        # Linear regression weights
        local_model = LogisticRegression()
        local_model.fit(perturbations, predictions, sample_weight=weights)

        # Get feature importance
        feature_weights = np.abs(local_model.coef_[0])
        top_indices = np.argsort(feature_weights)[-n_features:]

        return {
            'features': [feature_names[i] for i in top_indices],
            'weights': feature_weights[top_indices],
            'prediction': self.model.predict(instance.reshape(1, -1))[0]
        }

lime = SimpleLIME(rf_model, X_train)
lime_explanation = lime.explain_instance(X_test[0])

print(f"\nLIME Explanation for Sample 0:")
for feat, weight in zip(lime_explanation['features'], lime_explanation['weights']):
    print(f"  {feat}: {weight:.4f}")

# 5. Decision Tree Visualization
print("\n=== 5. Decision Tree Interpretation ===")

# Train small tree for visualization
small_tree = DecisionTreeClassifier(max_depth=3, random_state=42)
small_tree.fit(X_train, y_train)

print(f"Decision Tree (depth=3) trained")
print(f"Tree accuracy: {small_tree.score(X_test, y_test):.4f}")

# 6. Model-agnostic global explanations
print("\n=== 6. Global Model Behavior ===")

class GlobalExplainer:
    def __init__(self, model):
        self.model = model

    def get_prediction_distribution(self, X):
        """Analyze prediction distribution"""
        predictions = self.model.predict_proba(X)
        return {
            'class_0_mean': predictions[:, 0].mean(),
            'class_1_mean': predictions[:, 1].mean(),
            'class_1_std': predictions[:, 1].std()
        }

    def feature_sensitivity(self, X, feature_idx, n_perturbations=10):
        """Measure sensitivity to feature changes"""
        original_pred = self.model.predict_proba(X)[:, 1].mean()
        sensitivities = []

        for perturbation_level in np.linspace(0.1, 1.0, n_perturbations):
            X_perturbed = X.copy()
            X_perturbed[:, feature_idx] = np.random.normal(
                X[:, feature_idx].mean(),
                X[:, feature_idx].std() * perturbation_level,
                len(X)
            )
            perturbed_pred = self.model.predict_proba(X_perturbed)[:, 1].mean()
            sensitivities.append(abs(perturbed_pred - original_pred))

        return np.array(sensitivities)

explainer = GlobalExplainer(rf_model)
pred_dist = explainer.get_prediction_distribution(X_test)
print(f"\nPrediction Distribution:")
print(f"  Class 0 mean probability: {pred_dist['class_0_mean']:.4f}")
print(f"  Class 1 mean probability: {pred_dist['class_1_mean']:.4f}")

# 7. Visualization
print("\n=== 7. Explanability Visualizations ===")

fig, axes = plt.subplots(2, 3, figsize=(16, 10))

# 1. Feature Importance Comparison
top_features_plot = importance_df.head(10)
axes[0, 0].barh(top_features_plot['Feature'], top_features_plot['Impurity'], color='steelblue')
axes[0, 0].set_xlabel('Importance Score')
axes[0, 0].set_title('Feature Importance (Random Forest)')
axes[0, 0].invert_yaxis()

# 2. Permutation vs Impurity Importance
axes[0, 1].scatter(importance_df['Impurity'], importance_df['Permutation'], alpha=0.6)
axes[0, 1].set_xlabel('Impurity Importance')
axes[0, 1].set_ylabel('Permutation Importance')
axes[0, 1].set_title('Feature Importance Methods Comparison')
axes[0, 1].grid(True, alpha=0.3)

# 3. SHAP Values
shap_sorted = shap_df.head(10).sort_values('SHAP_Value')
colors = ['red' if x < 0 else 'green' for x in shap_sorted['SHAP_Value']]
axes[0, 2].barh(shap_sorted['Feature'], shap_sorted['SHAP_Value'], color=colors)
axes[0, 2].set_xlabel('SHAP Value')
axes[0, 2].set_title('SHAP Values for Sample 0')
axes[0, 2].axvline(x=0, color='black', linestyle='--', linewidth=0.8)

# 4. Partial Dependence
feature_0_idx = top_feature_indices[0]
feature_0_values = np.linspace(X_test[:, feature_0_idx].min(), X_test[:, feature_0_idx].max(), 50)
predictions_pd = []
for val in feature_0_values:
    X_temp = X_test.copy()
    X_temp[:, feature_0_idx] = val
    pred = rf_model.predict_proba(X_temp)[:, 1].mean()
    predictions_pd.append(pred)

axes[1, 0].plot(feature_0_values, predictions_pd, linewidth=2, color='purple')
axes[1, 0].set_xlabel(feature_names[feature_0_idx])
axes[1, 0].set_ylabel('Average Prediction (Class 1)')
axes[1, 0].set_title('Partial Dependence Plot')
axes[1, 0].grid(True, alpha=0.3)

# 5. Model Prediction Distribution
pred_proba = rf_model.predict_proba(X_test)[:, 1]
axes[1, 1].hist(pred_proba, bins=30, color='coral', edgecolor='black', alpha=0.7)
axes[1, 1].set_xlabel('Predicted Probability (Class 1)')
axes[1, 1].set_ylabel('Frequency')
axes[1, 1].set_title('Prediction Distribution')
axes[1, 1].grid(True, alpha=0.3, axis='y')

# 6. Feature Sensitivity Analysis
sensitivities = []
for feat_idx in range(min(5, X_test.shape[1])):
    sensitivity = explainer.feature_sensitivity(X_test, feat_idx, n_perturbations=5)
    sensitivities.append(sensitivity.mean())

axes[1, 2].bar(range(min(5, X_test.shape[1])), sensitivities, color='lightgreen', edgecolor='black')
axes[1, 2].set_xticks(range(min(5, X_test.shape[1])))
axes[1, 2].set_xticklabels([f'F{i}' for i in range(min(5, X_test.shape[1]))])
axes[1, 2].set_ylabel('Average Sensitivity')
axes[1, 2].set_title('Feature Sensitivity to Perturbations')
axes[1, 2].grid(True, alpha=0.3, axis='y')

plt.tight_layout()
plt.savefig('model_explainability.png', dpi=100, bbox_inches='tight')
print("\nVisualization saved as 'model_explainability.png'")

# 8. Summary
print("\n=== Explainability Summary ===")
print(f"Total Features Analyzed: {len(feature_names)}")
print(f"Most Important Feature: {importance_df.iloc[0]['Feature']}")
print(f"Importance Score: {importance_df.iloc[0]['Impurity']:.4f}")
print(f"Model Accuracy: {rf_model.score(X_test, y_test):.4f}")
print(f"Average Prediction Confidence: {pred_proba.mean():.4f}")

print("\nML model explanation setup completed!")

Explanation Techniques Comparison

• Feature Importance: Fast, global, model-specific
• SHAP: Theoretically sound, game-theory based, computationally expensive
• LIME: Model-agnostic, local explanations, interpretable
• PDP: Shows feature relationships, can be misleading with correlations
• Attention: Works for neural networks, interpretable attention weights

Interpretability vs Accuracy Trade-off

• Linear models: Highly interpretable, lower accuracy
• Tree models: Interpretable, moderate accuracy
• Neural networks: High accuracy, less interpretable
• Ensemble models: High accuracy, need explanation techniques

Regulatory Compliance

• GDPR: Right to explanation for automated decisions
• Fair Lending: Explainability for credit decisions
• Insurance: Transparency in underwriting
• Healthcare: Medical decision explanation

Deliverables

• Feature importance rankings
• Local explanations for predictions
• Partial dependence plots
• Global behavior analysis
• Model interpretation report
• Explanation dashboard