
Hi, 

I have a dataframe (try.1) with  date/time and temperature columns, and the date/time is in POSIXct fomat. Sample included below. 

I would like to to try decompose () or stl() to look at the trends and seasonality in my data, eventually so that  I can  look at autocorrelation.  The series is 3 years of water temperature with clearly visible seasonal periods. 

Right now, if I try decompose, I get the following error, w hich I beleive is because I haven't correctly defined a time series. 
"Error in decompose(try.1) : time series has no or less than 2 periods" 
  
I am stuck trying to go from POSIXct to as.ts 
Any suggestions on how to tackle this would be greatly appreciated.   

Sincerely, 
Mary Ann 

A sample of the data looks like this: 
'data.frame':	26925 obs. of  2 variables:
 $ date      : POSIXct, format: "2008-07-11 21:00:00" "2008-07-11 22:00:00" ...
 $ DL_1297699: num  15.3 15.1 14.9 14.6 14.1 ...   date DL_1297699 1 	2008-07-11 21:00:00 	15.318 
2 	2008-07-11 22:00:00 	15.127 
3 	2008-07-11 23:00:00 	14.888 
4 	2008-07-12 00:00:00 	14.553 
5 	2008-07-12 01:00:00 	14.146 
6 	2008-07-12 02:00:00 	13.738 
7 	2008-07-12 03:00:00 	13.401 
8 	2008-07-12 04:00:00 	13.088 
9 	2008-07-12 05:00:00 	12.823 
10 	2008-07-12 06:00:00 	12.630 and the dput(head(x,50) gives this output: structure(list(date = structure(c(1215810000, 1215813600, 1215817200, 
1215820800, 1215824400, 1215828000, 1215831600, 1215835200, 1215838800, 
1215842400, 1215846000, 1215849600, 1215853200, 1215856800, 1215860400, 
1215864000, 1215867600, 1215871200, 1215874800, 1215878400, 1215882000, 
1215885600, 1215889200, 1215892800, 1215896400, 1215900000, 1215903600, 
1215907200, 1215910800, 1215914400, 1215918000, 1215921600, 1215925200, 
1215928800, 1215932400, 1215936000, 1215939600, 1215943200, 1215946800, 
1215950400, 1215954000, 1215957600, 1215961200, 1215964800, 1215968400, 
1215972000, 1215975600, 1215979200, 1215982800, 1215986400), class = c("POSIXt", 
"POSIXct"), tzone = "UTC"), DL_1297699 = c(15.318, 15.127, 14.888, 
14.553, 14.146, 13.738, 13.401, 13.088, 12.823, 12.63, 12.461, 
12.413, 12.461, 12.703, 13.04, 13.497, 14.026, 14.553, 15.031, 
15.366, 15.7, 15.819, 15.819, 15.7, 15.605, 15.461, 15.247, 14.984, 
14.673, 14.337, 14.002, 13.666, 13.377, 13.137, 12.944, 12.823, 
12.847, 13.016, 13.329, 13.762, 14.242, 14.697, 15.175, 15.581, 
15.891, 16.034, 16.034, 15.939, 15.772, 15.581)), .Names = c("date", 
"DL_1297699"), row.names = c(NA, 50L), class = "data.frame") 



	[[alternative HTML version deleted]]

