ViewHandler extends ADDFFunctionalGroupHandler implements IHandleViews { @Override public DDF subset(List<Column> columnExpr, Expression filter) throws DDFException { DDF subset = _subset(columnExpr, filter); subset.getMetaDataHandler().copyFactor(this.getDDF(), this.getDDF().getColumnNames()); return subset; } ViewHandler(DDF theDDF); @Override List<Object[]> getRandomSample(int numSamples, boolean withReplacement, int seed); @Override DDF getRandomSampleByNum(int numSamples, boolean withReplacement,
                                  int seed); @Override DDF getRandomSample(double percent, boolean withReplacement, int seed); @Override List<String> head(int numRows); List<String> top(int numRows, String orderColumns, String mode); @Override DDF project(String... columnNames); @Override DDF project(List<String> columnNames); @Override DDF removeColumn(String columnName); @Override DDF removeColumns(String... columnNames); @Override DDF removeColumns(List<String> columnNames); @Override DDF subset(List<Column> columnExpr, Expression filter);  }
@Test public void testSubset() { }