.NET Core玩转机器学习

最近在搞机器学习，目前国内没有什么关于ML.NET的教程，官方都是一大堆英文，经过了我的努力，找到了Relax Development大哥的博客，有关于ML.NET的内容

原文地址：https://www.cnblogs.com/BeanHsiang/p/9010267.html

使用ML.NET直接从nuget中搜索ML.NET 安装到项目即可

去UCI Machine Learning Repository: Iris Data Set下载一个现成的数据集，复制粘贴其中的数据到任何一个文本编辑器中，然后保存命名为iris-data.txt到myApp目录中。

打开program.cs 以下代码：

using Microsoft.ML;
using Microsoft.ML.Runtime.Api;
using Microsoft.ML.Trainers;
using Microsoft.ML.Transforms;
using System;

namespace myApp
{
    class Program
    {
        // STEP 1: Define your data structures

        // IrisData is used to provide training data, and as
        // input for prediction operations
        // - First 4 properties are inputs/features used to predict the label
        // - Label is what you are predicting, and is only set when training
        public class IrisData
        {
            [Column("")]
            public float SepalLength;

            [Column("")]
            public float SepalWidth;

            [Column("")]
            public float PetalLength;

            [Column("")]
            public float PetalWidth;

            [Column("")]
            [ColumnName("Label")]
            public string Label;
        }

        // IrisPrediction is the result returned from prediction operations
        public class IrisPrediction
        {
            [ColumnName("PredictedLabel")]
            public string PredictedLabels;
        }

        static void Main(string[] args)
        {
            // STEP 2: Create a pipeline and load your data
            var pipeline = new LearningPipeline();

            // If working in Visual Studio, make sure the 'Copy to Output Directory'
            // property of iris-data.txt is set to 'Copy always'
            string dataPath = "iris-data.txt";
            pipeline.Add(new TextLoader<IrisData>(dataPath, separator: ","));

            // STEP 3: Transform your data
            // Assign numeric values to text in the "Label" column, because only
            // numbers can be processed during model training
            pipeline.Add(new Dictionarizer("Label"));

            // Puts all features into a vector
            pipeline.Add(new ColumnConcatenator("Features", "SepalLength", "SepalWidth", "PetalLength", "PetalWidth"));

            // STEP 4: Add learner
            // Add a learning algorithm to the pipeline.
            // This is a classification scenario (What type of iris is this?)
            pipeline.Add(new StochasticDualCoordinateAscentClassifier());

            // Convert the Label back into original text (after converting to number in step 3)
            pipeline.Add(new PredictedLabelColumnOriginalValueConverter() { PredictedLabelColumn = "PredictedLabel" });

            // STEP 5: Train your model based on the data set
            var model = pipeline.Train<IrisData, IrisPrediction>();

            // STEP 6: Use your model to make a prediction
            // You can change these numbers to test different predictions
            var prediction = model.Predict(new IrisData()
            {
                SepalLength = 3.3f,
                SepalWidth = 1.6f,
                PetalLength = 0.2f,
                PetalWidth = 5.1f,
            });

            Console.WriteLine($"Predicted flower type is: {prediction.PredictedLabels}");
        }
    }
}