question: @ Override public boolean input ( Instance instance ) { if ( getInputFormat ( ) == null ) { throw new IllegalStateException ( "No input instance format defined" ) ; } if ( m_NewBatch ) { resetQueue ( ) ; m_NewBatch = false ; } Instances outputFormat = outputFormatPeek ( ) ; double [ ] vals = new double [ outputFormat . numAttributes ( ) ] ; boolean inRange = false ; double lastVal = Utils . missingValue ( ) ; int i , j ; for ( i = 0 , j = 0 ; j < outputFormat . numAttributes ( ) ; i ++ ) { if ( m_DeltaCols . isInRange ( i ) && ( i != instance . classIndex ( ) ) ) { if ( inRange ) { if ( Utils . isMissingValue ( lastVal ) || instance . isMissing ( i ) ) { vals [ j ++ ] = Utils . missingValue ( ) ; } else { vals [ j ++ ] = instance . value ( i ) - lastVal ; } } else { inRange = true ; } lastVal = instance . value ( i ) ; } else { vals [ j ++ ] = instance . value ( i ) ; } } Instance inst = null ; if ( instance instanceof SparseInstance ) { inst = new SparseInstance ( instance . weight ( ) , vals ) ; } else { inst = new DenseInstance ( instance . weight ( ) , vals ) ; } inst . setDataset ( getOutputFormat ( ) ) ; copyValues ( inst , false , instance . dataset ( ) , getOutputFormat ( ) ) ; inst . setDataset ( getOutputFormat ( ) ) ; push ( inst ) ; return true ; }
target:  Input an instance for filtering. Ordinarily the instance is processed and made available for output immediately. Some filters require all instances be read before producing output.