def build_leaf(self, sample_indice):
mx = self.x[sample_indice].mean(0)
sx = self.x[sample_indice].std(0) + self.EPSILON
nx = (self.x[sample_indice] - mx) / sx
best_estimator = LassoCV(alphas=self.reg_lambda, cv=5, random_state=self.random_state)
best_estimator.fit(nx, self.y[sample_indice])
best_estimator.coef_ = best_estimator.coef_ / sx
best_estimator.intercept_ = best_estimator.intercept_ - np.dot(mx, best_estimator.coef_.T)
xmin = np.min(np.dot(self.x[sample_indice], best_estimator.coef_) + best_estimator.intercept_)
xmax = np.max(np.dot(self.x[sample_indice], best_estimator.coef_) + best_estimator.intercept_)
predict_func = lambda x: np.clip(best_estimator.predict(x), xmin, xmax)
best_impurity = self.get_loss(self.y[sample_indice], best_estimator.predict(self.x[sample_indice]))
return predict_func, best_estimator, best_impurity
def AdaptiveLasso(
X,
y,
CV=True,
fit_intercept=fit_intercept_default,
alpha=None,
coef=None, #the real coefficients if know those
verbose=False,
n_lasso_iterations=5,
):
"""
Example of adaptive Lasso to produce event sparser solutions
Adaptive lasso consists in computing many Lasso with feature
reweighting. It's also known as iterated L1.
Help with the implementation:
https://gist.github.com/agramfort/1610922
--- Example 1: Using generated data -----
from sklearn.datasets import make_regression
X, y, coef = make_regression(n_samples=306, n_features=8000, n_informative=50,
noise=0.1, shuffle=True, coef=True, random_state=42)
X /= np.sum(X ** 2, axis=0) # scale features
alpha = 0.1
model_al = sklm.AdaptiveLasso(
X,
y,
alpha = alpha,
coef = coef,
verbose = True
)
---- Example 2: Using simpler data ----
X,y = pdml.X_y(df_scaled,target_name)
model_al = sklm.AdaptiveLasso(
X,
y,
verbose = True
)
"""
if "pandas" in str(type(X)):
X = X.to_numpy()
if "pandas" in str(type(y)):
y = y.to_numpy()
# function that computes the absolute value square root of an input
def g(w):
return np.sqrt(np.abs(w))
#computes 1/(2*square_root(abs(w)))
def gprime(w):
return 1. / (2. * np.sqrt(np.abs(w)) + np.finfo(float).eps)
# Or another option:
# ll = 0.01
# g = lambda w: np.log(ll + np.abs(w))
# gprime = lambda w: 1. / (ll + np.abs(w))
n_samples, n_features = X.shape
def p_obj(w, alpha):
return 1. / (2 * n_samples) * np.sum(
(y - np.dot(X, w))**2) + alpha * np.sum(g(w))
weights = np.ones(n_features)
for k in range(n_lasso_iterations):
X_w = X / weights[np.newaxis, :]
if CV:
clf = LassoCV(
#alpha=alpha,
fit_intercept=fit_intercept)
else:
clf = Lasso(alpha=alpha, fit_intercept=fit_intercept)
clf.fit(X_w, y)
if CV:
curr_alpha = clf.alpha_
else:
curr_alpha = alpha
coef_ = clf.coef_ / weights
weights = gprime(coef_)
if verbose:
print(p_obj(coef_, curr_alpha)) # should go down
clf.coef_ = coef_
if verbose:
X_w = X / weights[np.newaxis, :]
print(f"Final R^2 score: {clf.score(X,y)}")
#print(np.mean((clf.coef_ != 0.0) == (coef != 0.0)))
return clf
