The importance of data preprocessing in model training

The importance of data preprocessing in model training and specific code examples

Introduction:

Training machine learning and deep learning models In the process, data preprocessing is a very important and essential link. The purpose of data preprocessing is to transform raw data into a form suitable for model training through a series of processing steps to improve the performance and accuracy of the model. This article aims to discuss the importance of data preprocessing in model training and give some commonly used data preprocessing code examples.

1. The importance of data preprocessing

1. Data cleaning

Data cleaning is the first step in data preprocessing, its purpose is to process the original Problems such as outliers, missing values, and noise in the data. Outliers refer to data points that are obviously inconsistent with normal data. If not processed, they may have a great impact on the performance of the model. Missing values refer to the situation where some data are missing in the original data. Common processing methods include deleting samples containing missing values, using the mean or median to fill missing values, etc. Noise refers to incomplete or erroneous information such as errors contained in the data. Removing noise through appropriate methods can improve the generalization ability and robustness of the model.

2. Feature selection

Feature selection is to select the most relevant features from the original data according to the needs of the problem to reduce model complexity and improve model performance. For high-dimensional data sets, too many features will not only increase the time and space consumption of model training, but also easily introduce noise and over-fitting problems. Therefore, reasonable feature selection is very critical. Commonly used feature selection methods include filtering, packaging, and embedding methods.

3. Data Standardization

Data standardization is to scale the original data according to a certain ratio so that it falls within a certain interval. Data standardization is often used to solve the problem of dimensional inconsistency between data features. When training and optimizing the model, features in different dimensions may have different importance, and data standardization can make features in different dimensions have the same proportion. Commonly used data standardization methods include mean-variance normalization and maximum-minimum normalization.

2. Code examples for data preprocessing

We take a simple data set as an example to show specific code examples for data preprocessing. Suppose we have a demographic data set that contains characteristics such as age, gender, income, etc., and a label column indicating whether to purchase a certain item.

import pandas as pd from sklearn.preprocessing import OneHotEncoder, StandardScaler from sklearn.feature_selection import SelectKBest, chi2 from sklearn.model_selection import train_test_split # 读取数据集 data = pd.read_csv("population.csv") # 数据清洗 data = data.dropna() # 删除包含缺失值的样本 data = data[data["age"] > 0] # 删除异常年龄的样本 # 特征选择 X = data.drop(["label"], axis=1) y = data["label"] selector = SelectKBest(chi2, k=2) X_new = selector.fit_transform(X, y) # 数据标准化 scaler = StandardScaler() X_scaled = scaler.fit_transform(X_new) # 数据集划分 X_train, X_test, y_train, y_test = train_test_split(X_scaled, y, test_size=0.2, random_state=42)

In the above code, we use the Pandas library to read the data set, and delete samples containing missing values through thedropna()method, throughdata["age"] > ; 0Select samples of normal age. Next, we use theSelectKBestmethod for feature selection, wherechi2means using the chi-square test for feature selection, andk=2means selecting the two most important feature. Then, we use theStandardScalermethod to standardize the data on the selected features. Finally, we use thetrain_test_splitmethod to divide the data set into a training set and a test set.

Conclusion:

The importance of data preprocessing in model training cannot be ignored. Through reasonable pre-processing steps such as data cleaning, feature selection and data standardization, the performance and accuracy of the model can be improved. This article shows the specific methods and steps of data preprocessing by giving a simple data preprocessing code example. It is hoped that readers can flexibly use data preprocessing technology in practical applications to improve the effect and application value of the model.

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