Document the possible output column names in scored DataView

[CESARDELATORRE]

Right now, these column/field names are kind of "secret names" that you need to know.
I don't think this is documented "end-to-end" in docs.microsoft.com, neither in the HOW to / CookBook.

We should have the following info available:

The purpose of the output columns in scored IDataView depends on the specific learning task being used:

Regression

• Label: Original regression value of the example.
• Score: Predicted regression value.

Binary Classification

• Label: Original Label of the example.
• Score: Raw score from the learner (e.g. value before applying sigmoid function to get probability).
• Probability: Probability of being in certain class
• PredictedLabel: Predicted class.

Multi-class Classification

• Label: Original Label of the example.
• Score: Its an array whose length is equal to number of classes and contains probability for each class.
• PredictedLabel: Predicted class.

Clustering

• Label: Original cluster Id of the example.
• Score: Its an array whose length is equal to number of clusters. It contains square distance from the cluster centeriod.
• PredictedLabel: Predicted cluster Id.

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This is related to the following issue requesting that info and raised at the ML.NET repo:
dotnet/machinelearning#376

This additional issue might also be related:
#5640

[mairaw]

@JRAlexander @luisquintanilla FYI - I just tagged it with the ML.NET Guide

[shmoradims]

I believe this issue is already addressed as part of 1.0 API reference documentation. Now all trainers have a sub-section in their remarks called input/output columns, where the types and definition of the input/output columns are clearly explained. E.g.: https://docs.microsoft.com/en-us/dotnet/api/microsoft.ml.trainers.averagedperceptrontrainer?view=ml-dotnet#input-and-output-columns

[JRAlexander]

Thanks, @shmoradims! I agree and am therefore closing.