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{
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"# 情感分析及数据集\n",
":label:`sec_sentiment`\n",
"\n",
"随着在线社交媒体和评论平台的快速发展,大量评论的数据被记录下来。这些数据具有支持决策过程的巨大潜力。\n",
"*情感分析*sentiment analysis)研究人们在文本中\n",
"(如产品评论、博客评论和论坛讨论等)“隐藏”的情绪。\n",
"它在广泛应用于政治(如公众对政策的情绪分析)、\n",
"金融(如市场情绪分析)和营销(如产品研究和品牌管理)等领域。\n",
"\n",
"由于情感可以被分类为离散的极性或尺度(例如,积极的和消极的),我们可以将情感分析看作一项文本分类任务,它将可变长度的文本序列转换为固定长度的文本类别。在本章中,我们将使用斯坦福大学的[大型电影评论数据集(large movie review dataset](https://ai.stanford.edu/~amaas/data/sentiment/)进行情感分析。它由一个训练集和一个测试集组成,其中包含从IMDb下载的25000个电影评论。在这两个数据集中,“积极”和“消极”标签的数量相同,表示不同的情感极性。\n"
]
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{
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"id": "7822039c",
"metadata": {
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"tab": [
"pytorch"
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},
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"source": [
"import os\n",
"import torch\n",
"from torch import nn\n",
"from d2l import torch as d2l"
]
},
{
"cell_type": "markdown",
"id": "76c1daa2",
"metadata": {
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},
"source": [
"## 读取数据集\n",
"\n",
"首先,下载并提取路径`../data/aclImdb`中的IMDb评论数据集。\n"
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "831081fb",
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"tab": [
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"source": [
"#@save\n",
"d2l.DATA_HUB['aclImdb'] = (\n",
" 'http://ai.stanford.edu/~amaas/data/sentiment/aclImdb_v1.tar.gz',\n",
" '01ada507287d82875905620988597833ad4e0903')\n",
"\n",
"data_dir = d2l.download_extract('aclImdb', 'aclImdb')"
]
},
{
"cell_type": "markdown",
"id": "a376611c",
"metadata": {
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"source": [
"接下来,读取训练和测试数据集。每个样本都是一个评论及其标签:1表示“积极”,0表示“消极”。\n"
]
},
{
"cell_type": "code",
"execution_count": 3,
"id": "4d08a828",
"metadata": {
"execution": {
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"text": [
"训练集数目: 25000\n",
"标签: 1 review: Zentropa has much in common with The Third Man, another noir\n",
"标签: 1 review: Zentropa is the most original movie I've seen in years. If y\n",
"标签: 1 review: Lars Von Trier is never backward in trying out new technique\n"
]
}
],
"source": [
"#@save\n",
"def read_imdb(data_dir, is_train):\n",
" \"\"\"读取IMDb评论数据集文本序列和标签\"\"\"\n",
" data, labels = [], []\n",
" for label in ('pos', 'neg'):\n",
" folder_name = os.path.join(data_dir, 'train' if is_train else 'test',\n",
" label)\n",
" for file in os.listdir(folder_name):\n",
" with open(os.path.join(folder_name, file), 'rb') as f:\n",
" review = f.read().decode('utf-8').replace('\\n', '')\n",
" data.append(review)\n",
" labels.append(1 if label == 'pos' else 0)\n",
" return data, labels\n",
"\n",
"train_data = read_imdb(data_dir, is_train=True)\n",
"print('训练集数目:', len(train_data[0]))\n",
"for x, y in zip(train_data[0][:3], train_data[1][:3]):\n",
" print('标签:', y, 'review:', x[0:60])"
]
},
{
"cell_type": "markdown",
"id": "35e114e6",
"metadata": {
"origin_pos": 8
},
"source": [
"## 预处理数据集\n",
"\n",
"将每个单词作为一个词元,过滤掉出现不到5次的单词,我们从训练数据集中创建一个词表。\n"
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "b833b646",
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"source": [
"train_tokens = d2l.tokenize(train_data[0], token='word')\n",
"vocab = d2l.Vocab(train_tokens, min_freq=5, reserved_tokens=['<pad>'])"
]
},
{
"cell_type": "markdown",
"id": "6592cc46",
"metadata": {
"origin_pos": 10
},
"source": [
"在词元化之后,让我们绘制评论词元长度的直方图。\n"
]
},
{
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"source": [
"d2l.set_figsize()\n",
"d2l.plt.xlabel('# tokens per review')\n",
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"source": [
"正如我们所料,评论的长度各不相同。为了每次处理一小批量这样的评论,我们通过截断和填充将每个评论的长度设置为500。这类似于 :numref:`sec_machine_translation`中对机器翻译数据集的预处理步骤。\n"
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{
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"id": "2d5d1601",
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"execution": {
"iopub.execute_input": "2023-08-18T07:04:46.667504Z",
"iopub.status.busy": "2023-08-18T07:04:46.666759Z",
"iopub.status.idle": "2023-08-18T07:04:53.619587Z",
"shell.execute_reply": "2023-08-18T07:04:53.618556Z"
},
"origin_pos": 13,
"tab": [
"pytorch"
]
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"torch.Size([25000, 500])\n"
]
}
],
"source": [
"num_steps = 500 # 序列长度\n",
"train_features = torch.tensor([d2l.truncate_pad(\n",
" vocab[line], num_steps, vocab['<pad>']) for line in train_tokens])\n",
"print(train_features.shape)"
]
},
{
"cell_type": "markdown",
"id": "dca33759",
"metadata": {
"origin_pos": 14
},
"source": [
"## 创建数据迭代器\n",
"\n",
"现在我们可以创建数据迭代器了。在每次迭代中,都会返回一小批量样本。\n"
]
},
{
"cell_type": "code",
"execution_count": 7,
"id": "454154e6",
"metadata": {
"execution": {
"iopub.execute_input": "2023-08-18T07:04:53.625971Z",
"iopub.status.busy": "2023-08-18T07:04:53.624962Z",
"iopub.status.idle": "2023-08-18T07:04:53.662071Z",
"shell.execute_reply": "2023-08-18T07:04:53.660909Z"
},
"origin_pos": 16,
"tab": [
"pytorch"
]
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"X: torch.Size([64, 500]) , y: torch.Size([64])\n",
"小批量数目: 391\n"
]
}
],
"source": [
"train_iter = d2l.load_array((train_features,\n",
" torch.tensor(train_data[1])), 64)\n",
"\n",
"for X, y in train_iter:\n",
" print('X:', X.shape, ', y:', y.shape)\n",
" break\n",
"print('小批量数目:', len(train_iter))"
]
},
{
"cell_type": "markdown",
"id": "42b492d4",
"metadata": {
"origin_pos": 18
},
"source": [
"## 整合代码\n",
"\n",
"最后,我们将上述步骤封装到`load_data_imdb`函数中。它返回训练和测试数据迭代器以及IMDb评论数据集的词表。\n"
]
},
{
"cell_type": "code",
"execution_count": 8,
"id": "8dd551a9",
"metadata": {
"execution": {
"iopub.execute_input": "2023-08-18T07:04:53.666983Z",
"iopub.status.busy": "2023-08-18T07:04:53.666388Z",
"iopub.status.idle": "2023-08-18T07:04:53.677743Z",
"shell.execute_reply": "2023-08-18T07:04:53.676460Z"
},
"origin_pos": 20,
"tab": [
"pytorch"
]
},
"outputs": [],
"source": [
"#@save\n",
"def load_data_imdb(batch_size, num_steps=500):\n",
" \"\"\"返回数据迭代器和IMDb评论数据集的词表\"\"\"\n",
" data_dir = d2l.download_extract('aclImdb', 'aclImdb')\n",
" train_data = read_imdb(data_dir, True)\n",
" test_data = read_imdb(data_dir, False)\n",
" train_tokens = d2l.tokenize(train_data[0], token='word')\n",
" test_tokens = d2l.tokenize(test_data[0], token='word')\n",
" vocab = d2l.Vocab(train_tokens, min_freq=5)\n",
" train_features = torch.tensor([d2l.truncate_pad(\n",
" vocab[line], num_steps, vocab['<pad>']) for line in train_tokens])\n",
" test_features = torch.tensor([d2l.truncate_pad(\n",
" vocab[line], num_steps, vocab['<pad>']) for line in test_tokens])\n",
" train_iter = d2l.load_array((train_features, torch.tensor(train_data[1])),\n",
" batch_size)\n",
" test_iter = d2l.load_array((test_features, torch.tensor(test_data[1])),\n",
" batch_size,\n",
" is_train=False)\n",
" return train_iter, test_iter, vocab"
]
},
{
"cell_type": "markdown",
"id": "ead6677a",
"metadata": {
"origin_pos": 22
},
"source": [
"## 小结\n",
"\n",
"* 情感分析研究人们在文本中的情感,这被认为是一个文本分类问题,它将可变长度的文本序列进行转换转换为固定长度的文本类别。\n",
"* 经过预处理后,我们可以使用词表将IMDb评论数据集加载到数据迭代器中。\n",
"\n",
"## 练习\n",
"\n",
"1. 我们可以修改本节中的哪些超参数来加速训练情感分析模型?\n",
"1. 请实现一个函数来将[Amazon reviews](https://snap.stanford.edu/data/web-Amazon.html)的数据集加载到数据迭代器中进行情感分析。\n"
]
},
{
"cell_type": "markdown",
"id": "0a0b32b5",
"metadata": {
"origin_pos": 24,
"tab": [
"pytorch"
]
},
"source": [
"[Discussions](https://discuss.d2l.ai/t/5726)\n"
]
}
],
"metadata": {
"language_info": {
"name": "python"
},
"required_libs": []
},
"nbformat": 4,
"nbformat_minor": 5
}