Thanks for everyone's input so far, it is greatly appreciated. But I've got
one last task I could use some advice on


Here are the first few lines of my data set:

site,time_local,time_utc,reef_type_code,sensor_type,sensor_depth_m,temperature_c
06,2006-04-09 10:20:00,2006-04-09 20:20:00,BAK,sb39, 2, 29.63
06,2006-04-09 10:40:00,2006-04-09 20:40:00,BAK,sb39, 2, 29.56
06,2006-04-09 11:00:00,2006-04-09 21:00:00,BAK,sb39, 2, 29.51
06,2006-04-09 11:20:00,2006-04-09 21:20:00,BAK,sb39, 10, 29.53
06,2006-04-09 11:40:00,2006-04-09 21:40:00,BAK,sb39, 2, 29.57
06,2006-04-09 12:00:00,2006-04-09 22:00:00,BAK,sb39, 2, 29.60
06,2006-04-09 12:20:00,2006-04-09 22:20:00,BAK,sb39, 2, 29.66
06,2006-04-09 12:40:00,2006-04-09 22:40:00,BAK,sb39, 2, 29.68
06,2006-04-09 13:00:00,2006-04-09 23:00:00,BAK,sb39, 10, 29.68
06,2006-04-09 13:20:00,2006-04-09 23:20:00,BAK,sb39, 2, 29.71
06,2006-04-09 13:40:00,2006-04-09 23:40:00,BAK,sb39, 2, 29.68
06,2006-04-09 14:00:00,2006-04-10 00:00:00,BAK,sb39, 10, 29.49
06,2006-04-09 14:20:00,2006-04-10 00:20:00,BAK,sb39, 2, 29.31
06,2006-04-09 14:40:00,2006-04-10 00:40:00,BAK,sb39, 10, 29.27

My goal was to extract all of the 10m data (all of the "10"'s from the
"sensor_depth_m" column) and than calculate daily averages.


With the help from this forum I came up with this:

library(zoo)
Data=read.table("06_BottomMountThermistors.csv",sep=",",header=TRUE,as.is
=TRUE)
Ten=subset(Data,sensor_depth_m==10L)
 z=zoo(Ten$temperature_c,Ten$time_local)
Warning message:
In zoo(Ten$temperature_c, Ten$time_local) :
  some methods for “zoo” objects do not work if the index entries in ‘
order.by’ are not unique
 ag=aggregate(zoo,as.Date,mean)
write.csv(ag,file="LTER_6_10m.csv")


Which works fine. I'm not sure why I get the error concerning unique
entries as all of the 10m "time local" data is sequential and thus unique.
Certainly some of the "temperature_c" data is repeated, but my
understanding of a zoo object is that I have the "time_local" column set up
as the order.by index.
So any thoughts on the warning message and my understanding of zoo objects
would be appreciated.

But the last task I have for this data is to average several of these data
sets together. My thoughts were to run the code as above for 6 different
sites (column 1 is the "site" index). I still think in excel, so I was
planning on lining up all 6 sites in a spreadsheet so that the dates (daily
means from the above code) line up, and then just averaging the data like
so:


Date, Site1, Site2, Site3, Site4, Site5, Site6   Average
2006-04-09 ,20,19,20,19,14,12,average(Site1-6)
2006-04-10,12,13,14,15,16,12 ,average(Site1-6)
2006-04-11,12,12,12,13,12,12 , average(Site1-6)
2006-04-12,12,13,13,12,12,12, average(Site1-6)


But I figure R can do this for me, so why bother going back to excel when R
is turning out to be a way better way to work with this kind of data. I
tried using merge, but I don't think this is the right command.
So is there anyway I can have R  take 6 different data sets, line them up
by date, and pull a grand average by day for all 6 sites?


Thanks again for all of your help. You guys rock!

	[[alternative HTML version deleted]]

