Machine Learning in Python Using Scikit-Learn: A Beginner&#s Guide-Python Tutorial-php.cn

Machine Learning in Python Using Scikit-Learn: A Beginner

Are you interested in learning about machine learning using Python? Look no further than the Scikit-Learn library! This popular python library is designed for efficient data mining, analysis, and model building. In this guide, we will introduce you to the basics of Scikit-Learn and how you can start using it for your machine learning projects.

What is Scikit-Learn?
Scikit-Learn is a powerful and easy-to-use tool for data mining and analysis. It is built on top of other popular libraries like NumPy, SciPy, and Matplotlib. It is open-source and has a commercially available BSD license, making it accessible for anyone to use.

What Can You Do with Scikit-Learn?
Scikit-Learn is widely used for three main tasks in machine learning:

1. Classification
Classification involves identifying which category an object belongs to. For example, predicting whether an email is spam or not.

2. Regression
Regression is the process of predicting a continuous variable based on relevant independent variables. For example, using past stock prices to predict future prices.

3. Clustering
Clustering involves grouping similar objects into different clusters automatically. For example, segmenting customers based on buying patterns.

How to Install Scikit-Learn?
If you are using a Windows operating system, here is a step-by-step guide to installing Scikit-Learn:

Install Python by downloading it from https://www.python.org/downloads/. Open the terminal by searching for ‘cmd’ and enter python --version to check the installed version.
Install NumPy by downloading the installer from https://sourceforge.net/projects/numpy/files/NumPy/1.10.2/.
Download the SciPy installer fromSciPy: Scientific Library for Python - Browse /scipy/0.16.1 at SourceForge.net.
Install Pip by typing python get_pip.py in the command line terminal.
Finally, install scikit-learn by typing pip install scikit-learn in the command line.

What is a Scikit Data Set?
A Scikit data set is a built-in dataset provided by the library for users to practice and test their models. You can find the names of these data sets at https://scikit-learn.org/stable/datasets/index.html. For this guide, we will be using the wine quality-red data set, which can also be downloaded from Kaggle.

Importing the Data Set and Modules
To start using Scikit-Learn, we first need to import the necessary modules and the data set.

Import the pandas module and use the read_csv() method to read .csv file and convert it into a pandas DataFrame.

The modules we will be using are:

NumPy for algebraic and numerical calculations
Pandas for working with data frames
The model_selection module to select between different models
The preprocessing module for scaling and transforming our data
The RandomForestRegressor to compare performance metrics of our data set

Training Sets and Test Sets
Splitting the data into training and test sets is crucial for estimating your model's performance. The training set is used to build and test our algorithm, while the test set is used to evaluate the accuracy of our predictions.

To split our data, we will use the train_test_split() function provided by Scikit-Learn.

Preprocessing Data
Preprocessing data is the initial and most important step that enhances the quality of a model. It involves making the data suitable for use in a machine learning model.

One common preprocessing technique is standardization, which standardizes the range of input data features before applying machine learning models. For this, we can use the Transformer API provided by Scikit-Learn.

Understanding Hyperparameters and Cross-Validation
Hyperparameters are higher-level concepts, such as complexity and learning rate, that cannot be directly learned from the data and need to be predefined.

To assess a model's generalization performance and avoid overfitting, cross-validation is an important evaluation technique. This involves dividing the data set into N random parts with equal volume.

Evaluating Model Performance
After training and testing our model, it's time to evaluate its performance using various metrics. For this, we will import the metrics we need, such as r2_score and mean_squared_error.

r2_score 関数は独立変数の従属変数の分散を計算し、mean_squared_error は誤差の二乗の平均を計算します。パフォーマンスが十分であるかどうかを判断するには、モデルの目標を念頭に置くことが重要です。

今後使用するためにモデルを保存することを忘れないでください!

結論として、Python での機械学習に Scikit-Learn を使用する基本を説明しました。このガイドで概説されている手順に従うことで、独自のデータマイニングおよび分析プロジェクトで Scikit-Learn の調査と使用を開始できます。ユーザーフレンドリーなインターフェイスと幅広い機能を備えた Scikit-Learn は、初心者にも経験豊富なデータサイエンティストにも同様に強力なツールです。

MyExamCloud で利用可能な Python 認定模擬テストを使用して、Python コーディング能力を向上させます。

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