Merge pull request #18126 from danielenricocahall:add-oob-error-sample-weighting

Account for sample weights in calculating OOB Error

* account for sample weights in oob error calculation

* redefine oob error functions

* fix ABI compatibility

modules/ml/include/opencv2/ml.hpp

@@ -1294,6 +1294,15 @@ public:
     */
     CV_WRAP void getVotes(InputArray samples, OutputArray results, int flags) const;
 
+    /** Returns the OOB error value, computed at the training stage when calcOOBError is set to true.
+     * If this flag was set to false, 0 is returned. The OOB error is also scaled by sample weighting.
+     */
+#if CV_VERSION_MAJOR == 3
+    CV_WRAP double getOOBError() const;
+#else
+    /*CV_WRAP*/ virtual double getOOBError() const = 0;
+#endif
+
     /** Creates the empty model.
     Use StatModel::train to train the model, StatModel::train to create and train the model,
     Algorithm::load to load the pre-trained model.