[R] Help with creating a ts (time series) object with daily sampling values

From: Pamela Allen <pallen_at_hatfieldgroup.com>
Date: Thu, 24 Mar 2011 12:24:22 -0700 (PDT)


Hi All,  

I have a data set of daily measurements of river flow. I would like to create a "ts" object from this data.  

Here's a sample data set:

date <- as.Date(c(1:300), format="%Y")

year=as.numeric(format(date, format = "%Y"))

month=as.numeric(format(date, format = "%m"))

julianday=as.numeric(format(date, format = "%j"))

week=floor(julianday/7)

flow <- sin(2*pi/53*c(1:300))

data <- cbind.data.frame(date,year,month,julianday,week, flow)  

I know how to do this with exact dates using the irts package:

install.packages("tseries")

library(tseries)

data=cbind.data.frame(data,posixlt.time=as.POSIXlt(data$date, "PDT")) ##To create dates based on POSIXlt

data.irts=irts(data$posixlt.time, data$flow)  

But I would like the time series object to be in the "ts" format. I tried using this code:  

data.ts=ts(data$flow, start=c(data$year[1], data$julianday[1]), frequency=365)  

Which does work, but I worry about the influence of leap years, since my data set is quite large. What is the way to properly code a ts object with daily measurements? Thank you!  

-Pam  

Pam Allen

Vancouver, BC  



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