[R] time series problem: time points don't match

[Brad Patrick Schneid]

Hi, 
I have a time series problem that I would like some help with if you have
the time.  I have many data from many sites that look like this:  

Site.1
date		time		level           temp
2009/10/01 00:01:52.0      2.8797      18.401
2009/10/01 00:16:52.0      2.8769      18.382
2009/10/01 00:31:52.0      2.8708      18.309
2009/10/01 00:46:52.0      2.8728      18.285
2009/10/01 01:01:52.0      2.8716      18.245
2009/10/01 01:16:52.0      2.8710      18.190

Site.2
date		time		level          temp
2009/10/01 00:11:06.0      2.9507      18.673
2009/10/01 00:26:06.0      2.9473      18.630
2009/10/01 00:41:06.0      2.9470      18.593
2009/10/01 00:56:06.0      2.9471      18.562
2009/10/01 01:11:06.0      2.9451      18.518
2009/10/01 01:26:06.0      2.9471      18.480

As you can see, the times do not match up.  What I would like to do is be
able to merge these two data sets to the nearest time stamp by creating a
new time between the two; something like this:


date		new.time	level.1       temp.1    level.2         temp.2
2009/10/01 00:01:52.0      2.8797      18.401	NA	       NA
2009/10/01 00:13:59.0      2.8769      18.382      2.9507      18.673
2009/10/01 00:28:59.0      2.8708      18.309      2.9473      18.630
2009/10/01 00:43:59.0      2.8728      18.285      2.9470      18.593
2009/10/01 00:59:59.0      2.8716      18.245     2.9471      18.562
2009/10/01 01:13:59.0      2.8710      18.190     2.9451      18.518
2009/10/01 01:26:06.0       NA              NA          2.9471      18.480

Note that the sites may not match in the # of observations and a return of
NA would be necessary, but a deletion of that time point all together for
both sites would be preferred.

A possibly easier alternative would be a way to assign generic times for
each observation according to the time interval, so that the 1st observation
for each day would have a time = 00:00:00 and each consecutive one would be
15 minutes later.   

Thanks for any suggestions.

Brad

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