[SPARK-1406] Throw IllegalArgumentException when exporting a multinomial

logistic regression

Author: selvinsource

mllib/src/main/scala/org/apache/spark/mllib/pmml/export/PMMLModelExportFactory.scala

@@ -44,7 +44,11 @@ private[mllib] object PMMLModelExportFactory {
         new GeneralizedLinearPMMLModelExport(svm,
           "linear SVM: if predicted value > 0, the outcome is positive, or negative otherwise")
       case logistic: LogisticRegressionModel =>
-        new LogisticRegressionPMMLModelExport(logistic, "logistic regression")
+        if(logistic.numClasses == 2)
+          new LogisticRegressionPMMLModelExport(logistic, "logistic regression")
+        else
+          throw new IllegalArgumentException(
+            "PMML Export not supported for Multinomial Logistic Regression")
       case _ =>
         throw new IllegalArgumentException(
           "PMML Export not supported for model: " + model.getClass.getName)

mllib/src/test/scala/org/apache/spark/mllib/pmml/export/PMMLModelExportFactorySuite.scala

@@ -73,6 +73,18 @@ class PMMLModelExportFactorySuite extends FunSuite {
 
     assert(logisticRegressionModelExport.isInstanceOf[LogisticRegressionPMMLModelExport])
   }
+  
+  test("PMMLModelExportFactory throw IllegalArgumentException "
+    + "when passing a Multinomial Logistic Regression") {
+    /** 3 classes, 2 features */
+    val multiclassLogisticRegressionModel = new LogisticRegressionModel(
+      weights = Vectors.dense(0.1, 0.2, 0.3, 0.4), intercept = 1.0, 
+      numFeatures = 2, numClasses = 3)
+    
+    intercept[IllegalArgumentException] {
+      PMMLModelExportFactory.createPMMLModelExport(multiclassLogisticRegressionModel)
+    }
+  }
 
   test("PMMLModelExportFactory throw IllegalArgumentException when passing an unsupported model") {
     val invalidModel = new Object