ML .NET 二手车价格预测之评估（三）

在模型生成后，可以通过Evaluate方法进行评估

//注意，这里使用txt或者tsv格式的文件
string testCsvPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "TrainData", "test-data2.txt");
string modelDirectory = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Model");
string modelPath = Path.Combine(modelDirectory, "UsedCarsPricePredictionMLModel.zip");

MLContext mlContext = new MLContext(seed: 0);

ITransformer loadedModel = mlContext.Model.Load(modelPath, out _);

var testDataView = mlContext.Data.LoadFromTextFile(testCsvPath, hasHeader: true);
//https://docs.microsoft.com/zh-cn/dotnet/api/microsoft.ml.data.regressionmetrics?view=ml-dotnet&WT.mc_id=DT-MVP-5003010
var testMetrics = mlContext.Regression.Evaluate(loadedModel.Transform(testDataView), labelColumnName: "Price");

//获取模型的绝对损失
vm.MeanAbsoluteError = testMetrics.MeanAbsoluteError;
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