Python_机器学习_李宏毅老师作业二

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# Author:Richard
import numpy as np
import matplotlib.pyplot as plt

np.random.seed(0)  # 使得每次生成的随机数相同
X_train_path = r"G:\课程学习\机器学习\Mr_Li_ML\HomeWorks\数据\hw2\data\X_train"
Y_train_path = r"G:\课程学习\机器学习\Mr_Li_ML\HomeWorks\数据\hw2\data\Y_train"
X_test_path = r"G:\课程学习\机器学习\Mr_Li_ML\HomeWorks\数据\hw2\data\X_test"

# 将数据转成numpy格式
with open(X_train_path) as File:
    head = next(File)  # 提取投文件，Str格式
    # print(type(head),head[0])
    X_train = np.array([line.strip('\n').split(',')[1:] for line in File], dtype=float)
    # print(X_train.shape)  #(54256,510)
with open(Y_train_path) as File:
    head = next(File)
    Y_train = np.array([line.strip('\n').split(',')[1] for line in File], dtype=float)
    # print(Y_train.shape)  #(5425611)
with open(X_test_path) as File:
    head = next(File)
    X_test = np.array([line.strip('\n').split(',')[1:] for line in File], dtype=float)
    # print(X_test.shape)   #(27622,510)


# set a Normalize function
def _normalize(X, train=True, specified_column=None, X_mean=None, X_std=None):
    # This function normalizes specific columns of X.
    # The mean and standard variance of training data will be reused when processing testing data.
    #
    # Arguments:
    #     X: data to be processed
    #     train: 'True' when processing training data, 'False' for testing data
    #     specific_column: indexes of the columns that will be normalized. If 'None', all columns
    #         will be normalized.
    #     X_mean: mean value of training data, used when train = 'True'
    #     X_std: standard deviation of training data, used when train = 'True'
    # Outputs:
    #     X: normalized data
    #     X_mean: computed mean value of training data
    #     X_std: computed standard deviation of training data
    if specified_column == None:
        specified_column = np.arange(X.shape[1])
    if train:
        X_mean = np.mean(X[:, specified_column], axis=0)
        X_std = np.std(X[:, specified_column], axis=0)
    for i in range(X.shape[0]):
        for j in range(X.shape[1]):
            if X_std[j] != 0:
                X[i, j] = (X[i, j] - X_mean[j]) / X_std[j]
    return X, X_mean, X_std


# 标准化训练数据和测试数据
X_train, X_mean, X_std = _normalize(X_train, train=True)
X_test, _, _ = _normalize(X_test, train=False, X_mean=X_mean, X_std=X_std)
# _变量用来存储函数返回的无用值
# 将数据分成训练集和验证集  9:1
ratio = 0.9
train_len = int(len(X_train) * ratio)
# X_train = X_train[:train_len]
# Y_train = Y_train[:train_len]
# X_dev = X_train[train_len:]
# Y_dev = Y_train[train_len:]

X_train0 = X_train
Y_train0 = Y_train
X_train = X_train0[:train_len]
Y_train = Y_train0[:train_len]
X_dev = X_train0[train_len:]
Y_dev = Y_train0[train_len:]

#
train_size = X_train.shape[0]
dev_size = X_dev.shape[0]
test_size = X_test.shape[0]
data_dim = X_train.shape[1]


# print('Size of training set: {}'.format(train_size))
# print('Size of development set: {}'.format(dev_size))
# print('Size of testing set: {}'.format(test_size))
# print('Dimension of data: {}'.format(data_dim))
###

# Size of training set: 48830
# Size of development set: 5426
# Size of testing set: 27622
# imension of data: 510
###

def _shuffle(X, Y):
    # This function shuffles two equal-length list/array, X and Y, together.
    randomize = np.arange(len(X))
    np.random.shuffle(randomize)
    return (X[randomize], Y[randomize])


def _sigmoid(z):
    # sigmoid function can be used to calculate probability
    # to avoid overflow, min/max value is set
    return np.clip(1.0 / (1.0 + np.exp(-z)), 1e-8, 1 - 1e-8)


def _f(X, w, b):
    # This is the logistic regression function, parameterized by w and b
    #
    # Arguements:
    #     X: input data, shape = [batch_size, data_dimension]
    #     w: weight vector, shape = [data_dimension, ]
    #     b: bias, scalar
    # Output:  numpy.matmul 函数返回两个数组的矩阵乘积
    #     predicted probability of each row of X being positively labeled, shape = [batch_size, ]
    return _sigmoid(np.matmul(X, w) + b)


def _predict(X, w, b):
    # This function returns a truth value prediction for each row of X
    # by rounding the result of logistic regression function.
    # return np.round(_f(X,w,b)).astype(np.int)  #原则：对于浮点型数据，四舍六入，正好一半就搞到偶数，和文中说的不太一样 修改
    # return 1 if _f(X, w, b) >= 0.5 else 0
    f = _f(X, w, b)
    f[f >= 0.5] = 1
    f[f < 0.5] = 0
    return f


def _accuracy(Y_pred, Y_label):
    # this function calculate presiction accuracy
    acc = 1 - np.mean(np.abs(Y_pred - Y_label))
    # acc = 1 - np.abs(Y_pred - Y_label)
    return acc


def _cross_entropy_loss(Y_pred, Y_label):
    # This function computes the cross entropy.
    #
    # Arguements:
    #     y_pred: probabilistic predictions, float vector
    #     Y_label: ground truth labels, bool vector
    # Output:
    #     cross entropy, scalar
    cross_entropy = -np.dot(Y_label, np.log(Y_pred)) - np.dot((1 - Y_label), np.log(1 - Y_pred))
    return cross_entropy


def _gradient(X, Y_label, w, b):
    # This function computes the gradient of cross entropy loss with respect to weight w and bias b.
    y_pred = _f(X, w, b)
    pred_error = Y_label - y_pred
    w_grad = -np.sum(pred_error * X.T, 1)
    b_grad = -np.sum(pred_error)
    return w_grad, b_grad


# 初始化权重w和b 都为0
w = np.zeros((data_dim,))
b = np.zeros((1,))
# 训练时的超参数
max_iter = 20
batch_size = 8
learning_rate = 0.05
# 保存每个iteration的loss和accuracy,方便画图
train_loss = []
dev_loss = []
train_acc = []
dev_acc = []
# 累计参数更新的次数
step = 1
# 迭代训练
for epoch in range(max_iter):
    # 在每个epoch开始时，随机打散训练数据
    X_train, Y_train = _shuffle(X_train, Y_train)
    # Mini-batch训练
    for idx in range(int(np.floor(train_size / batch_size))):
        X = X_train[idx * batch_size:(idx + 1) * batch_size]
        Y = Y_train[idx * batch_size:(idx + 1) * batch_size]
        # calculate gradient
        # 学习率随着时间衰减
        w_grad, b_grad = _gradient(X, Y, w, b)
        w = w - learning_rate / np.sqrt(step) * w_grad
        b = b - learning_rate / np.sqrt(step) * b_grad
        #
        step += 1
    # 计算训练集合测试集的loss和accuracy
    # Y_train_pred = _predict(X_train, w, b)
    # for i in range(len(Y_train_pred)):
    #     train_acc.append(_accuracy(Y_train_pred[i], Y_train[i]))
    #     train_loss.append(_cross_entropy_loss(Y_train_pred[i], Y_train[i]) / train_size)
    # Y_dev_pred = _predict(X_dev, w, b)
    # for i in range(len(Y_dev_pred)):
    #     dev_acc.append(_accuracy(Y_dev_pred[i], Y_dev[i]))
    #     dev_loss.append(_cross_entropy_loss(Y_dev_pred[i], Y_dev[i]) / dev_size)
    y_train_pred = _f(X_train, w, b)
    # Y_train_pred = np.round(y_train_pred)
    Y_train_pred = _predict(X_train, w, b)
    train_acc.append(_accuracy(Y_train_pred, Y_train))
    train_loss.append(_cross_entropy_loss(y_train_pred, Y_train) / train_size)

    y_dev_pred = _f(X_dev, w, b)
    # Y_dev_pred = np.round(y_dev_pred)
    Y_dev_pred = _predict(X_dev, w, b)
    dev_acc.append(_accuracy(Y_dev_pred, Y_dev))
    dev_loss.append(_cross_entropy_loss(y_dev_pred, Y_dev) / dev_size)

print('Training loss: {}'.format(train_loss[-1]))
print('Development loss: {}'.format(dev_loss[-1]))
print('Training accuracy: {}'.format(train_acc[-1]))
print('Development accuracy: {}'.format(dev_acc[-1]))

print('weight_hw2.npy', w)
# Loss curve
plt.plot(train_loss)
plt.plot(dev_loss)
plt.title("Loss")
plt.legend(['train', 'dev'])
plt.show()

# accuracy curve
plt.plot(train_acc)
plt.plot(dev_acc)
plt.title("Accuracy")
plt.legend(['train', 'dev'])
plt.show()

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