takes the logfiles and produces an event summary matrix
            date        command result  process source
            20140421    9       40      178     9
            20140423    0       0       6       0
            20140424    19      1       47      19
            20140425    24      0       117     24
            20140426    16      0       83      16
            20140427    1       0       6       1
            20140429    0       0       0       4

def summarise_events(self):
        """
        takes the logfiles and produces an event summary matrix
            date        command result  process source
            20140421    9       40      178     9
            20140423    0       0       6       0
            20140424    19      1       47      19
            20140425    24      0       117     24
            20140426    16      0       83      16
            20140427    1       0       6       1
            20140429    0       0       0       4

        """
        all_dates = []
        d_command = self._count_by_date(self.command_file, all_dates)
        d_result  = self._count_by_date(self.result_file,  all_dates)
        d_process = self._count_by_date(self.process_file, all_dates)
        d_source  = self._count_by_date(self.source_file,  all_dates)

        with open(self.log_sum, "w") as sum_file:
            sum_file.write('date,command,result,process,source\n')
            for dte in sorted(set(all_dates)):
                sum_file.write(dte + ',')
                if dte in d_command:
                    sum_file.write(str(d_command[dte]) + ',')
                else:
                    sum_file.write('0,')
                if dte in d_result:
                    sum_file.write(str(d_result[dte]) + ',')
                else:
                    sum_file.write('0,')
                if dte in d_process:
                    sum_file.write(str(d_process[dte]) + ',')
                else:
                    sum_file.write('0,')
                if dte in d_source:
                    sum_file.write(str(d_source[dte]) + '\n')
                else:
                    sum_file.write('0\n')