[R] Code for finding successive mean

[Kwabena Fosu-Amankwah]

Hi am Kwabena,

I would be very grateful if someone can help me with the code or script on
how to find successive mean at 30 minutes interval for the set of data
below:

Date/Time PR     SW TP  SM SHF CO2
28.11.2011 17:39:49 978.4 13.15 30.5 20 NA NA
28.11.2011 17:50:00 978.5 13.11 30.4 20 NA NA
28.11.2011 18:00:00 978.8 13.14 30.3 20 NA NA
28.11.2011 18:10:00 979 13.07 30.1 20 NA NA
28.11.2011 18:20:00 979.2 13.1 30 20 NA NA
28.11.2011 18:30:00 979.4 13.09 29.8 20 NA NA
28.11.2011 18:40:00 979.5 13.08 29.6 20 NA NA
28.11.2011 18:50:00 979.5 13.06 29.5 20 NA NA
28.11.2011 19:00:00 979.6 13.06 29.4 20 NA NA
28.11.2011 19:10:00 979.7 13.05 29.3 20 NA NA
28.11.2011 19:20:00 979.9 13.03 29.2 20 NA NA
28.11.2011 19:30:00 980 13 29.1 20 NA NA
28.11.2011 19:40:00 980 13.03 29 20 NA NA
28.11.2011 19:50:00 980.1 13.03 28.9 20 NA NA
28.11.2011 20:00:00 980.3 13      28.8 20 NA NA
28.11.2011 20:10:00 980.5 12.97 28.7 20 NA NA
28.11.2011 20:20:00 980.8 12.96 28.6 20 NA NA
28.11.2011 20:30:00 981.1 12.95 28.5 20 NA NA
28.11.2011 20:40:00 981.1 12.95 28.4 20 NA NA
28.11.2011 20:50:00 981.2 12.94 28.3 20 NA NA
28.11.2011 21:00:00 981.3 12.93 28.2 20 NA NA
28.11.2011 21:10:00 981.3 12.92 28.1 20 NA NA
28.11.2011 21:20:00 981.5 12.9 28 20 NA NA
28.11.2011 21:30:00 981.6 12.9    27.9 20 NA NA
28.11.2011 21:40:00 981.7 12.88 27.9 20 NA NA
28.11.2011 21:50:00 981.7 12.87 27.8 20 NA NA
28.11.2011 22:00:00 981.7 12.86 27.7 20 NA NA
28.11.2011 22:10:00 981.8 12.85 27.6 20 NA NA
28.11.2011 22:20:00 981.8 12.84 27.5 20 NA NA
28.11.2011 22:30:00 981.8 12.83 27.5 20 NA NA

Thank you

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