def log_change_ratio(old_node: DecisionNode, old_left_node: LeafNode,
old_right_node: LeafNode, node: LeafNode,
left_node: LeafNode, right_node: LeafNode, sigma: Sigma,
sigma_mu: float):
var = np.power(sigma.current_value(), 2)
var_mu = np.power(sigma_mu, 2)
n_1 = old_left_node.data.n_obsv
n_1_star = left_node.data.n_obsv
n_2 = old_right_node.data.n_obsv
n_2_star = old_right_node.data.n_obsv
combined_y_sum, left_y_sum, right_y_sum = left_and_right_sums(
old_node, old_left_node, old_right_node)
combined_y_sum_star, left_y_sum_star, right_y_sum_star = left_and_right_sums(
node, left_node, right_node)
first_term = (var / var_mu + n_1) / (var / var_mu + n_1_star) * (
var / var_mu + n_2) / (var / var_mu + n_2_star)
first_term = np.log(np.sqrt(first_term))
left_contribution = np.square(left_y_sum) / (n_1 + var / var_mu)
right_contribution = np.square(right_y_sum) / (n_2 + var / var_mu)
left_contribution_star = np.square(left_y_sum_star) / (n_1_star +
var / var_mu)
right_contribution_star = np.square(right_y_sum_star) / (n_2_star +
var / var_mu)
contribution = left_contribution_star + right_contribution_star - left_contribution - right_contribution
return first_term + contribution / (2 * var)
def log_grow_ratio(combined_node: LeafNode, left_node: LeafNode,
right_node: LeafNode, sigma: Sigma, sigma_mu: float):
var = np.power(sigma.current_value(), 2)
var_mu = np.power(sigma_mu, 2)
n = combined_node.data.n_obsv
n_l = left_node.data.n_obsv
n_r = right_node.data.n_obsv
first_term = (var * (var + n * sigma_mu)) / ((var + n_l * var_mu) *
(var + n_r * var_mu))
first_term = np.log(np.sqrt(first_term))
if combined_node.data.y_sum_cache_up_to_date and left_node.data.y_sum_cache_up_to_date:
combined_y_sum = combined_node.data.summed_y()
left_y_sum = left_node.data.summed_y()
right_y_sum = right_node.data.summed_y()
else:
combined_y_sum = combined_node.data.summed_y()
left_y_sum = left_node.data.summed_y()
right_y_sum = combined_y_sum - left_y_sum
left_resp_contribution = np.square(left_y_sum) / (var + n_l * sigma_mu)
right_resp_contribution = np.square(right_y_sum) / (var + n_r * sigma_mu)
combined_resp_contribution = np.square(combined_y_sum) / (var +
n * sigma_mu)
resp_contribution = left_resp_contribution + right_resp_contribution - combined_resp_contribution
return first_term + ((var_mu / (2 * var)) * resp_contribution)
def log_grow_ratio(combined_node: LeafNode, left_node: LeafNode, right_node: LeafNode, sigma: Sigma, sigma_mu: float):
var = np.power(sigma.current_value(), 2)
var_mu = np.power(sigma_mu, 2)
n = combined_node.data.n_obsv
n_l = left_node.data.n_obsv
n_r = right_node.data.n_obsv
first_term = (var * (var + n * sigma_mu)) / ((var + n_l * var_mu) * (var + n_r * var_mu))
first_term = np.log(np.sqrt(first_term))
left_resp_contribution = np.square(np.sum(left_node.data.y)) / (var + n_l * sigma_mu)
right_resp_contribution = np.square(np.sum(right_node.data.y)) / (var + n_r * sigma_mu)
combined_resp_contribution = np.square(np.sum(combined_node.data.y)) / (var + n * sigma_mu)
resp_contribution = left_resp_contribution + right_resp_contribution - combined_resp_contribution
return first_term + ((var_mu / (2 * var)) * resp_contribution)