[R] help with time series

[Steve_Friedman at nps.gov]

Hello everyone


I'm working with R 2.8.1 on a windows  machine

I have a question regarding time series analysis

The first question is how does R expect the input file to be structured?
I'm working with a *.txt file similar to the abbreviated one here:

Date,stage
4/2/1953,7.56
4/3/1953,7.56
4/4/1953,7.54
4/5/1953,7.53
4/6/1953,7.5
4/7/1953,7.47
4/8/1953,7.44
4/9/1953,7.41
4/10/1953,7.37
4/11/1953,7.33
4/12/1953,7.3
4/13/1953,7.26
4/14/1953,7.28
4/15/1953,7.28
4/16/1953,7.23
4/17/1953,7.47
4/18/1953,7.59
4/19/1953,7.58
4/20/1953,7.57
4/21/1953,7.56
4/22/1953,7.55
4/23/1953,7.53
4/24/1953,7.51
4/25/1953,7.48
4/26/1953,7.46
4/27/1953,7.5
4/28/1953,7.56

The data record is substantially longer - 50 years worth of daily
hydrologic water stage data  (column 2).

R seems to get confused by the format of this input not knowing what to do
with the date field, and also deciding to treat everything as a level.

I'm reading the data as follows:

mystage <- read.table("C:\\Documents and
Settings\\skfriedman\\Desktop\\R-scripts\\stage.txt", header = TRUE)

looking at the data  I get the following:

 mystage[1:4,]
[1] 4/2/1953,7.56 4/3/1953,7.56 4/4/1953,7.54 4/5/1953,7.53
20195 Levels: 1/1/1954,8.72 1/1/1955,8.48 1/1/1956,7.94 1/1/1957,7.88
1/1/1958,8.5 ... 9/9/2007,8.84
>

What I'd like is a time series  with a starting data of April 21, 1953.
ending December 30, 2008.  data are daily records, so the frequency should
be 365 (?) not counting leap year nuisances.

So the first question is how should I build the input file to correctly
import it to a time series with an odd beginning date?

The analysis I'm really trying to get to will involve calculating the mean
monthly stage, the mean seasonal (aggregated over several months) stage,
the annual maximum period with a continuous stage greater than 0.

Thanks in advance I will summary solutions.

Much appreciated

Steve

Steve Friedman Ph. D.
Spatial Statistical Analyst
Everglades and Dry Tortugas National Park
950 N Krome Ave (3rd Floor)
Homestead, Florida 33034

Steve_Friedman at nps.gov
Office (305) 224 - 4282
Fax     (305) 224 - 4147