TrainTestSplit should be inside MLContext.Data

[ganik]

fixes #2337

[artidoro]

// The .NET Foundation licenses this file to you under the MIT license.

Could you update the MlNetCookBook.md for both dynamic and static?

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Refers to: test/Microsoft.ML.Tests/Scenarios/Api/CookbookSamples/CookbookSamples.cs:2 in c1be3c8. [](commit_id = c1be3c8, deletion_comment = False)

[codecov]

Codecov Report

Merging #2905 into master will increase coverage by <.01%.
The diff coverage is 94.33%.

@@            Coverage Diff             @@
##           master    #2905      +/-   ##
==========================================
+ Coverage    71.8%   71.81%   +<.01%     
==========================================
  Files         812      812              
  Lines      142644   142643       -1     
  Branches    16090    16090              
==========================================
+ Hits       102432   102436       +4     
+ Misses      35828    35824       -4     
+ Partials     4384     4383       -1

Flag	Coverage Δ
#Debug	71.81% <94.33%> (ø)	⬆️
#production	67.95% <93.61%> (ø)	⬆️
#test	86.25% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
src/Microsoft.ML.Data/TrainCatalog.cs	84.11% <ø> (-1.72%)	⬇️
...icrosoft.ML.StaticPipe/TrainingStaticExtensions.cs	27.92% <ø> (ø)	⬆️
...rosoft.ML.StaticPipelineTesting/StaticPipeTests.cs	95.27% <ø> (-0.01%)	⬇️
test/Microsoft.ML.Functional.Tests/Prediction.cs	100% <100%> (ø)	⬆️
test/Microsoft.ML.Functional.Tests/Validation.cs	100% <100%> (ø)	⬆️
...s/Scenarios/Api/CookbookSamples/CookbookSamples.cs	99.49% <100%> (ø)	⬆️
...est/Microsoft.ML.StaticPipelineTesting/Training.cs	99.37% <100%> (ø)	⬆️
...s/Api/CookbookSamples/CookbookSamplesDynamicApi.cs	93.62% <100%> (ø)	⬆️
test/Microsoft.ML.Tests/Scenarios/Api/TestApi.cs	97.6% <100%> (ø)	⬆️
...soft.ML.Data/DataLoadSave/DataOperationsCatalog.cs	72.26% <93.61%> (+11.15%)	⬆️
... and 4 more

[artidoro]

Looks good! And the fact that the it used to be in the base training catalog makes me thing this was a good change. Please make sure to update the cookbooks before checking in.