LearningPipeline.Execute must have a Data step as the last step

[Btjones711]

System information

• OS version/distro: windows 10
• .NET Version (eg., dotnet --info):
  .Net 7.1

Issue

I am getting this error: LearningPipeline.Execute must have a Data step as the last step
When trying to create my pipeline following along the "Tutorial: Use ML.NET to predict New York Taxi Fares (Regression)" tutorial.

Source code / logs

Here is my class and main program code:

TermDate.cs
public class TerminationDate
{
[Column(ordinal: "0")]
public float age;
[Column(ordinal: "1")]
public float gender;
[Column(ordinal: "2")]
public float married;
[Column(ordinal: "3")]
public float salary;
[Column(ordinal: "4")]
public float TermYear;
}

public class TermDatePrediction
{
    [Column("Score")]
    public float TermYear;
}

part of Program.cs
class Program
{
const string _datapath = @"......\Data\Book1.csv";
const string _testdatapath = @"......\Data\Book2.csv";
const string _modelpath = @"......\Models\Model.zip";
static async Task Main(string[] args)
{
PredictionModel<TerminationDate, TermDatePrediction> modelTerm = await Train();
Evaluate(modelTerm);
var predictionTerm = modelTerm.Predict(TestTerminations.Term1);
Console.WriteLine("Predicted Year: {0}", predictionTerm.TermYear);
Console.ReadLine();
}

    public static async Task<PredictionModel<TerminationDate, TermDatePrediction>> Train()
    {
        var pipeline = new LearningPipeline
        {
            new TextLoader<TerminationDate>(_datapath, useHeader: true, separator: ","),
            new ColumnCopier(("TermYear","Label")),
            new ColumnConcatenator("Features", "age", "gender", "married", "salary"),
            new FastTreeRegressor()
        };
        PredictionModel<TerminationDate, TermDatePrediction> modelTerm = pipeline.Train<TerminationDate, TermDatePrediction>();
        await modelTerm.WriteAsync(_modelpath);
        return modelTerm;
    }

    private static void Evaluate(PredictionModel<TerminationDate, TermDatePrediction> model)
    {
        var testData = new TextLoader<TerminationDate>(_testdatapath, useHeader: true, separator: ",");
        var evaluator = new RegressionEvaluator();
        RegressionMetrics metrics = evaluator.Evaluate(model, testData);
        Console.WriteLine("RMS=" + metrics.Rms);
        Console.WriteLine("R^2=" + metrics.RSquared);
    }
}

[codemzs]

@Btjones711 Did this happen when you tried the debugger extension?

[Btjones711]

I am not sure what you mean by that. My visual studio is in debug mode and if I step through I can see the error if I view pipeline after it is initialized. If I remove all the async stuff the program works.

Thanks!

[rasodu]

I was trying out something similar. I see the same error in pipeline.Rows after I add trainer to the pipeline. I am using visual studio code for debugging.
This is the code after I see the error:

pipeline.Add(new FastTreeRegressor());

This is the error message:

"System.InvalidOperationException: LearningPipeline.Execute must have a Data step as the last step.\n   at Microsoft.ML.LearningPipeline.Execute(IHostEnvironment environment)\n   at Microsoft.ML.LearningPipelineDebugProxy.ExecutePipeline()"

Also, I only see first 10 rows even though the dataset is much larger.

Is LearningPipelineDebugProxy some kind of view on actual data which is simply here to help during debugging? Does it stop showing data after you add a step that is not data step? Does running pipeline in debugging mode effect the final model in anyway?
LearningPipelineDebugProxy.cs

[jwood803]

I'm seeing this as well and my pipeline is exactly the same as @Btjones711 but with different data.

If it helps, when viewing the pipeline in the debugger I get the below:

[yehia2amer]

I am getting the Same Error: System.InvalidOperationException: LearningPipeline.Execute must have a Data step as the last step. at Microsoft.ML.LearningPipeline.Execute(IHostEnvironment environment) at Microsoft.ML.LearningPipelineDebugProxy.ExecutePipeline()
Any Hints why !

[shriganesh1987]

I am also getting this error:
pipeline.Rows[0] = "System.InvalidOperationException: LearningPipeline.Execute must have a Data step as the last step.\r\n at Microsoft.ML.LearningPipeline.Execute(IHostEnvironment environment)\r\n at Microsoft.ML.LearningPipelineDebugProxy.ExecutePipeline()"

[otsomkalov]

Same for me:

It happens when i'm debug my code step-by-step.
If i trying run my code i'm getting exception:

[danmoseley]

@shauheen seems several people are stuck here.

[codemzs]

Looking at this.

[doughutchens]

I hit the same issue. Cloned the repo and debugged it. It occurs when the trainer (new FastTreeRegressor() in my case) is added to the list of ILearningPipelineItem items.

Training the model and evaluating it appears to work from the output below:
Processed 768 instances
Binning and forming Feature objects
Reserved memory for tree learner: 107536 bytes
Starting to train ...
Not training a calibrator because it is not needed.
Rms = 1.00680682114123
RSquared = 0.995004854767641

It is the Rows and Columns variables that are disappearing from the DebuggerTypeProxy values attached to the LearningPipeline instance in VS.

I found this note on MSDN in regards to the DebuggerTypeProxyAttribute. Use this attribute when you need to significantly and fundamentally change the debugging view of a type, but not change the type itself.

Build: 0.4-preview-26705

[Pat02]

I am still having the problem described above.

	Name	Value	Type
▶	[0]	"System.InvalidOperationException: LearningPipeline.Execute must have a Data step as the last step.\r\n at Microsoft.ML.LearningPipeline.Execute(IHostEnvironment environment)\r\n at Microsoft.ML.LearningPipelineDebugProxy.ExecutePipeline()"	Microsoft.ML.PipelineItemDebugRow

is there any update on the fix?
My code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.ML.Runtime.Api;
using Microsoft.ML.Models;
using Microsoft.ML.Trainers;
using Microsoft.ML.Transforms;
using Microsoft.ML;
using Microsoft.ML.Data;
using System;

namespace ConsoleApp1
{
class Program
{
static void Main(string[] args)
{
var pipeline = new LearningPipeline();

        pipeline.Add(new TextLoader("TestDataCSV.csv").CreateFrom<SalaryData>(useHeader: true, separator:char.Parse(",")));
        pipeline.Add(new ColumnConcatenator("Features", "years"));
        pipeline.Add(new GeneralizedAdditiveModelRegressor());  //<-- Error occurs on this line

        var model = pipeline.Train<SalaryData,PredictedSalary>();

        var testdata = new TextLoader("TestDataCSVtestdata.csv").CreateFrom<SalaryData>(useHeader: true, separator: char.Parse(","));
        var evaluator = new RegressionEvaluator();
        var metrics = evaluator.Evaluate(model, testdata);
    }
}

class SalaryData
{
    [Column("0")]
    public double years;

    [Column("1")]
    public double wage;
}

class PredictedSalary
{
    [Column("0")]
    public double score;
}

}

[Pat02]

Found this in the source code, that's where the Error is thrown. None of the tutorials or videos I've seen are having this issue, but I can't tell what I'm doing differently.