312 lines
12 KiB
Plaintext
312 lines
12 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# 机器学习100天——第1天：数据预处理（Data Preprocessing）"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"搭建anaconda环境，参考 https://zhuanlan.zhihu.com/p/33358809\n",
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"\n",
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"## 第一步：导入需要的库\n",
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"这两个是我们每次都需要导入的库。NumPy包含数学计算函数。Pandas用于导入和管理数据集。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 42,
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"metadata": {},
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"outputs": [],
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"source": [
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"import numpy as np\n",
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"import pandas as pd"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"[[ 7. 2. 3. ]\n [ 4. 3.5 6. ]\n [10. 3.5 9. ]]\nSklearn verion is 0.23.1\n"
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]
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}
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],
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"source": [
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"import sklearn\n",
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"from sklearn.impute import SimpleImputer\n",
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"#This block is an example used to learn SimpleImputer\n",
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"imp_mean = SimpleImputer(missing_values=np.nan, strategy='mean')\n",
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"imp_mean.fit([[7, 2, 3], [4, np.nan, 6], [10, 5, 9]])\n",
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"X = [[np.nan, 2, 3], [4, np.nan, 6], [10, np.nan, 9]]\n",
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"print(imp_mean.transform(X))\n",
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"print(\"Sklearn verion is {}\".format(sklearn.__version__))"
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]
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},
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{
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"source": [
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"from sklearn.preprocessing import OneHotEncoder\n",
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"enc = OneHotEncoder(handle_unknown='ignore')\n",
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"X = [['Male', 1], ['Female', 3], ['Female', 2]]\n",
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">>> enc.fit(X)\n",
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"OneHotEncoder(handle_unknown='ignore')\n",
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">>> enc.categories_\n",
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"[array(['Female', 'Male'], dtype=object), array([1, 2, 3], dtype=object)]\n",
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">>> enc.transform([['Female', 1], ['Male', 4]]).toarray()\n",
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"array([[1., 0., 1., 0., 0.],\n",
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" [0., 1., 0., 0., 0.]])\n",
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">>> enc.inverse_transform([[0, 1, 1, 0, 0], [0, 0, 0, 1, 0]])\n",
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"array([['Male', 1],\n",
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" [None, 2]], dtype=object)\n",
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">>> enc.get_feature_names(['gender', 'group'])\n",
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"array(['gender_Female', 'gender_Male', 'group_1', 'group_2', 'group_3'],\n",
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" dtype=object)"
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],
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"cell_type": "code",
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"metadata": {},
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"execution_count": 4,
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"outputs": [
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{
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"output_type": "error",
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"ename": "SyntaxError",
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"evalue": "invalid syntax (<ipython-input-4-44f585aeb41d>, line 4)",
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"traceback": [
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"\u001b[1;36m File \u001b[1;32m\"<ipython-input-4-44f585aeb41d>\"\u001b[1;36m, line \u001b[1;32m4\u001b[0m\n\u001b[1;33m >>> enc.fit(X)\u001b[0m\n\u001b[1;37m ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m invalid syntax\n"
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]
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}
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 第二步：导入数据集\n",
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"数据集通常是.csv格式。CSV文件以文本形式保存表格数据。文件的每一行是一条数据记录。我们使用Pandas的read_csv方法读取本地csv文件为一个数据帧。然后，从数据帧中制作自变量和因变量的矩阵和向量。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 52,
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"metadata": {},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"Step 2: Importing dataset\nX\n[['France' 44.0 72000.0]\n ['Spain' 27.0 48000.0]\n ['Germany' 30.0 54000.0]\n ['Spain' 38.0 61000.0]\n ['Germany' 40.0 nan]\n ['France' 35.0 58000.0]\n ['Spain' nan 52000.0]\n ['France' 48.0 79000.0]\n ['Germany' 50.0 83000.0]\n ['France' 37.0 67000.0]]\nY\n['No' 'Yes' 'No' 'No' 'Yes' 'Yes' 'No' 'Yes' 'No' 'Yes']\n[[44.0 72000.0]\n [27.0 48000.0]\n [30.0 54000.0]\n [38.0 61000.0]\n [40.0 nan]\n [35.0 58000.0]\n [nan 52000.0]\n [48.0 79000.0]\n [50.0 83000.0]\n [37.0 67000.0]]\n"
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]
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}
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],
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"source": [
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"dataset = pd.read_csv('../datasets/Data.csv')\n",
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"# 不包括最后一列的所有列\n",
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"X = dataset.iloc[ : , :-1].values\n",
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"#取最后一列\n",
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"Y = dataset.iloc[ : , 3].values\n",
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"print(\"Step 2: Importing dataset\")\n",
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"print(\"X\")\n",
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"print(X)\n",
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"print(\"Y\")\n",
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"print(Y)\n",
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"print(X[ : , 1:3])"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 第三步：处理丢失数据\n",
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"我们得到的数据很少是完整的。数据可能因为各种原因丢失，为了不降低机器学习模型的性能，需要处理数据。我们可以用整列的平均值或中间值替换丢失的数据。我们用sklearn.preprocessing库中的Imputer类完成这项任务。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 53,
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"metadata": {},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"---------------------\nStep 3: Handling the missing data\nstep2\nX\n[['France' 44.0 72000.0]\n ['Spain' 27.0 48000.0]\n ['Germany' 30.0 54000.0]\n ['Spain' 38.0 61000.0]\n ['Germany' 40.0 63777.77777777778]\n ['France' 35.0 58000.0]\n ['Spain' 38.77777777777778 52000.0]\n ['France' 48.0 79000.0]\n ['Germany' 50.0 83000.0]\n ['France' 37.0 67000.0]]\n"
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]
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}
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],
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"source": [
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"# If you use the newest version of sklearn, use the lines of code commented out\n",
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"from sklearn.impute import SimpleImputer\n",
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"imputer = SimpleImputer(missing_values=np.nan, strategy=\"mean\")\n",
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"#from sklearn.preprocessing import Imputer\n",
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"# axis=0表示按列进行\n",
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"#imputer = Imputer(missing_values = \"NaN\", strategy = \"mean\", axis = 0)\n",
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"#print(imputer)\n",
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"#\n",
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"# print(X[ : , 1:3])\n",
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"imputer = imputer.fit(X[ : , 1:3]) #put the data we want to process in to this imputer\n",
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"X[ : , 1:3] = imputer.transform(X[ : , 1:3]) #replace the np.nan with mean\n",
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"#print(X[ : , 1:3])\n",
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"print(\"---------------------\")\n",
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"print(\"Step 3: Handling the missing data\")\n",
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"print(\"step2\")\n",
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"print(\"X\")\n",
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"print(X)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 第四步：解析分类数据\n",
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"分类数据指的是含有标签值而不是数字值的变量。取值范围通常是固定的。例如\"Yes\"和\"No\"不能用于模型的数学计算，所以需要解析成数字。为实现这一功能，我们从sklearn.preprocessing库导入LabelEncoder类。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 54,
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"metadata": {},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"---------------------\nStep 4: Encoding categorical data\nX\n[[1.0 0.0 0.0 44.0 72000.0]\n [0.0 0.0 1.0 27.0 48000.0]\n [0.0 1.0 0.0 30.0 54000.0]\n [0.0 0.0 1.0 38.0 61000.0]\n [0.0 1.0 0.0 40.0 63777.77777777778]\n [1.0 0.0 0.0 35.0 58000.0]\n [0.0 0.0 1.0 38.77777777777778 52000.0]\n [1.0 0.0 0.0 48.0 79000.0]\n [0.0 1.0 0.0 50.0 83000.0]\n [1.0 0.0 0.0 37.0 67000.0]]\nY\n[0 1 0 0 1 1 0 1 0 1]\n"
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]
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}
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],
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"source": [
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"from sklearn.preprocessing import LabelEncoder, OneHotEncoder\n",
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"from sklearn.compose import ColumnTransformer \n",
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"#labelencoder_X = LabelEncoder()\n",
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"#X[ : , 0] = labelencoder_X.fit_transform(X[ : , 0])\n",
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"#Creating a dummy variable\n",
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"#print(X)\n",
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"ct = ColumnTransformer([(\"\", OneHotEncoder(), [0])], remainder = 'passthrough')\n",
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"X = ct.fit_transform(X)\n",
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"#onehotencoder = OneHotEncoder(categorical_features = [0])\n",
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"#X = onehotencoder.fit_transform(X).toarray()\n",
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"labelencoder_Y = LabelEncoder()\n",
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"Y = labelencoder_Y.fit_transform(Y)\n",
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"print(\"---------------------\")\n",
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"print(\"Step 4: Encoding categorical data\")\n",
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"print(\"X\")\n",
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"print(X)\n",
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"print(\"Y\")\n",
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"print(Y)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 第五步：拆分数据集为测试集合和训练集合\n",
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"把数据集拆分成两个：一个是用来训练模型的训练集合，另一个是用来验证模型的测试集合。两者比例一般是80:20。我们导入sklearn.model_selection库中的train_test_split()方法。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 55,
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"metadata": {},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"---------------------\nStep 5: Splitting the datasets into training sets and Test sets\nX_train\n[[0.0 1.0 0.0 40.0 63777.77777777778]\n [1.0 0.0 0.0 37.0 67000.0]\n [0.0 0.0 1.0 27.0 48000.0]\n [0.0 0.0 1.0 38.77777777777778 52000.0]\n [1.0 0.0 0.0 48.0 79000.0]\n [0.0 0.0 1.0 38.0 61000.0]\n [1.0 0.0 0.0 44.0 72000.0]\n [1.0 0.0 0.0 35.0 58000.0]]\nX_test\n[[0.0 1.0 0.0 30.0 54000.0]\n [0.0 1.0 0.0 50.0 83000.0]]\nY_train\n[1 1 1 0 1 0 0 1]\nY_test\n[0 0]\n"
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]
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}
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],
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"source": [
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"from sklearn.model_selection import train_test_split\n",
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"X_train, X_test, Y_train, Y_test = train_test_split( X , Y , test_size = 0.2, random_state = 0)\n",
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"print(\"---------------------\")\n",
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"print(\"Step 5: Splitting the datasets into training sets and Test sets\")\n",
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"print(\"X_train\")\n",
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"print(X_train)\n",
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"print(\"X_test\")\n",
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"print(X_test)\n",
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"print(\"Y_train\")\n",
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"print(Y_train)\n",
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"print(\"Y_test\")\n",
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"print(Y_test)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 第六步：特征量化\n",
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"大部分模型算法使用两点间的欧氏距离表示，但此特征在幅度、单位和范围姿态问题上变化很大。在距离计算中，高幅度的特征比低幅度特征权重更大。可用特征标准化或Z值归一化解决。导入sklearn.preprocessing库的StandardScalar类。"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 57,
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"metadata": {},
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"outputs": [
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{
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"output_type": "stream",
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"name": "stdout",
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"text": [
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"---------------------\nStep 6: Feature Scaling\nX_train\n[[-1. 2.64575131 -0.77459667 0.26306757 0.12381479]\n [ 1. -0.37796447 -0.77459667 -0.25350148 0.46175632]\n [-1. -0.37796447 1.29099445 -1.97539832 -1.53093341]\n [-1. -0.37796447 1.29099445 0.05261351 -1.11141978]\n [ 1. -0.37796447 -0.77459667 1.64058505 1.7202972 ]\n [-1. -0.37796447 1.29099445 -0.0813118 -0.16751412]\n [ 1. -0.37796447 -0.77459667 0.95182631 0.98614835]\n [ 1. -0.37796447 -0.77459667 -0.59788085 -0.48214934]]\nX_test\n[[-1. 2.64575131 -0.77459667 -1.45882927 -0.90166297]\n [-1. 2.64575131 -0.77459667 1.98496442 2.13981082]]\n"
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]
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}
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],
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"source": [
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"from sklearn.preprocessing import StandardScaler\n",
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"sc_X = StandardScaler()\n",
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"X_train = sc_X.fit_transform(X_train)\n",
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"X_test = sc_X.transform(X_test) #we should not use fit_transfer cause the u and z is determined from x_train\n",
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"print(\"---------------------\")\n",
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"print(\"Step 6: Feature Scaling\")\n",
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"print(\"X_train\")\n",
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"print(X_train)\n",
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"print(\"X_test\")\n",
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"print(X_test)\n"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"<b>完整的项目请前往Github项目<a href=\"https://github.com/MachineLearning100/100-Days-Of-ML-Code\">100-Days-Of-ML-Code</a>查看。有任何的建议或者意见欢迎在issue中提出~</b>"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"name": "python3",
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"display_name": "Python 3.8.3 64-bit (conda)",
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"metadata": {
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"interpreter": {
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"hash": "1b78ff499ec469310b6a6795c4effbbfc85eb20a6ba0cf828a15721670711b2c"
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}
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}
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.8.3-final"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 2
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} |