helpers.py
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	# -- coding: utf-8 --
	"""some helper functions."""

	import numpy as np


	def load_data():
	"""load data."""
	data = np.loadtxt("dataEx3.csv", delimiter=",", skiprows=1, unpack=True)
	x = data[0]
	y = data[1]
	return x, y


	def load_data_from_ex02(sub_sample=True, add_outlier=False):
	"""Load data and convert it to the metric system."""
	path_dataset = "height_weight_genders.csv"
	data = np.genfromtxt(
	path_dataset, delimiter=",", skip_header=1, usecols=[1, 2])
	height = data[:, 0]
	weight = data[:, 1]
	gender = np.genfromtxt(
	path_dataset, delimiter=",", skip_header=1, usecols=[0],
	converters={0: lambda x: 0 if b"Male" in x else 1})
	# Convert to metric system
	height *= 0.025
	weight *= 0.454

	# sub-sample
	if sub_sample:
	height = height[::50]
	weight = weight[::50]

	if add_outlier:
	# outlier experiment
	height = np.concatenate([height, [1.1, 1.2]])
	weight = np.concatenate([weight, [51.5/0.454, 55.3/0.454]])

	return height, weight, gender


	def standardize(x):
	"""Standardize the original data set."""
	mean_x = np.mean(x)
	x = x - mean_x
	std_x = np.std(x)
	x = x / std_x
	return x, mean_x, std_x


	def build_model_data(height, weight):
	"""Form (y,tX) to get regression data in matrix form."""
	y = weight
	x = height
	num_samples = len(y)
	tx = np.c_[np.ones(num_samples), x]
	return y, tx