how to calculate an average of data per day at txt file in matlab?

YY MM DD hh mm WDIR WSPD GST WVHT DPD APD MWD PRES ATMP WTMP DEWP VIS TIDE yr mo dy hr mn degT m/s m/s m sec sec deg hPa degC degC degC nmi ft 2013 08 31 23 50 353 1.3 1.9 0.96 7.69 6.24 286 1013.4 16.2 17.1 999.0 99.0 99.00 2013 09 01 00 50 104 1.6 2.1 1.08 7.14 6.74 275 1013.2 16.0 17.3 999.0 99.0 99.00 2013 09 01 01 50 143 1.7 2.1 1.06 14.81 6.52 219 1013.0 15.8 17.2 999.0 99.0 99.00 2013 09 01 02 50 133 1.4 2.7 0.95 13.79 6.21 224 1012.7 15.7 17.1 999.0 99.0 99.00 2013 09 01 03 50 149 2.8 3.7 0.91 13.79 6.27 211 1012.9 15.5 17.0 999.0 99.0 99.00 2013 09 01 04 50 168 3.5 4.2 0.89 13.79 6.24 224 1013.5 15.5 17.0 999.0 99.0 99.00 2013 09 01 05 50 220 3.5 4.1 0.95 14.81 6.67 157 1013.4 16.1 17.0 999.0 99.0 99.00 2013 09 01 06 50 192 3.1 3.7 0.95 13.79 6.95 121 1013.3 16.3 17.0 999.0 99.0 99.00