returns a flag array of the data loaded from a given file pattern
        
        :parameter pattern: pattern to match in the file list.

def get_file(self,pattern):
        '''
        returns a flag array of the data loaded from a given file pattern
        
        :parameter pattern: pattern to match in the file list. 
        '''
        flag=[fnmatch.fnmatch(l,pattern) for l in self.filelist]
        id=self.fid_list.compress(flag)
        flag = self.fileid == id
        return flag