[GitHub] azagrebin commented on a change in pull request #6425: [FLINK-9664][Doc] fixing documentation in ML quick start

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azagrebin commented on a change in pull request #6425: [FLINK-9664][Doc] fixing documentation in ML quick start
URL: https://github.com/apache/flink/pull/6425#discussion_r208576999
 
 

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 File path: docs/dev/libs/ml/quickstart.md
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 @@ -129,6 +129,10 @@ and the [test set here](http://www.csie.ntu.edu.tw/~cjlin/libsvmtools/datasets/b
 This is an astroparticle binary classification dataset, used by Hsu et al. [[3]](#hsu) in their
 practical Support Vector Machine (SVM) guide. It contains 4 numerical features, and the class label.
 
+Before importing the traning and test dataset, Flink SVM only supports threshold binary values of 
+`+1.0` and `-1.0`. Thus a conversion is needed upon downloading the svmguide1 dataset since it is 
+labelled using `1`s and `0`s.
+
 
 Review comment:
   I think this section belongs to the beginning of the next one `Classification`, because it is about LibSVM format.
   The code example of conversion could be also provided to make the example fully 'copy-paste' runnable.
   Small thing is also typo in `traning` -> `training`.
   
   I would suggest to modify the code example in this `LibSVM files` section like this:
   ```
   val astroTrainLibSVM: DataSet[LabeledVector] = MLUtils.readLibSVM(env, "/path/to/svmguide1")
   val astroTestLibSVM: DataSet[LabeledVector] = MLUtils.readLibSVM(env, "/path/to/svmguide1.t")
   ```
   to have no SVM training specifics here, and add something like this to the beginning of `Classification` section:
   
   _... After importing the training and test dataset, the data needs to be prepared for the classification, because Flink SVM only supports ... conversion is needed after downloading ..._
   And then the code example:
   ```
   def svmNormaliser : LabeledVector => LabeledVector =
       lv => LabeledVector(if (lv.label > 0.0) 1.0 else -1.0, lv.vector)
   val astroTrain: DataSet[LabeledVector] = astroTrainLibSVM.map(svmNormaliser)
   val astroTest: DataSet[(Vector, Double)] = astroTestLibSVM.map(svmNormaliser).map(x => (x.vector, x.label))
   ```

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