question: protected Instance mergeInstances ( Instance source , Instance dest ) { Instances outputFormat = outputFormatPeek ( ) ; double [ ] vals = new double [ outputFormat . numAttributes ( ) ] ; for ( int i = 0 ; i < vals . length ; i ++ ) { if ( ( i != outputFormat . classIndex ( ) ) && ( m_SelectedCols . isInRange ( i ) ) ) { if ( ( source != null ) && ! source . isMissing ( i ) && ! dest . isMissing ( i ) ) { vals [ i ] = dest . value ( i ) - source . value ( i ) ; } else { vals [ i ] = Utils . missingValue ( ) ; } } else { vals [ i ] = dest . value ( i ) ; } } Instance inst = null ; if ( dest instanceof SparseInstance ) { inst = new SparseInstance ( dest . weight ( ) , vals ) ; } else { inst = new DenseInstance ( dest . weight ( ) , vals ) ; } inst . setDataset ( dest . dataset ( ) ) ; return inst ; }
target:  Creates a new instance the same as one instance (the "destination") but with some attribute values copied from another instance (the "source")