Ансамбль деревьев

function permutation_importance(trees, X, y, n_repeats=5)
    n_features = size(X, 2)
    n_samples = size(X, 1)
    n_trees = length(trees)
    importance = zeros(n_features)
    baseline_pred = predict_ensemble(trees, X)
    valid_idx = .!isnan.(baseline_pred)
    
    if sum(valid_idx) == 0
        #error("Нет валидных базовых предсказаний")
    end
    
    baseline_mse = mean((y[valid_idx] - baseline_pred[valid_idx]).^2)
    
    for f in 1:n_features
        f_importance = 0.0
        for _ in 1:n_repeats
            X_perm = copy(X)
            perm_idx = randperm(n_samples)
            X_perm[:, f] = X[perm_idx, f]
            perm_pred = predict_ensemble(trees, X_perm)
            valid_perm_idx = valid_idx .& .!isnan.(perm_pred)
            
            if sum(valid_perm_idx) > 0
                perm_mse = mean((y[valid_perm_idx] - perm_pred[valid_perm_idx]).^2)
                f_importance += (perm_mse - baseline_mse)
            end
        end
        importance[f] = f_importance / n_repeats
    end
    
    return importance
end