[R] using its to import time series data with uneven dates

[Gabor Grothendieck]

On 7/12/05, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> On 7/12/05, Sheri Conner Gausepohl <sheri at atmos.colostate.edu> wrote:
> > Good day:
> >
> > I am trying to use
> > readcsvIts("nwr_data_qc.txt",informat=its.format("%Y%m%d%h%M
> > %Y"),header=TRUE,sep="",skip=0,row.names=NULL,as.is=TRUE,dec=".")
> >
> > to read in a file (nwr_data_qc.txt)  that looks like this:
> >
> > Time         Y      M   D  H   Min    CO2
> > 2000.18790   2000.  3.  9. 18. 30.    373.60
> > 2000.20156   2000.  3. 14. 18. 30.    373.34
> > 2000.22609   2000.  3. 23. 18.  0.    373.01
> >
> > and  R returns this:
> >
> >         Y  M  D  H Min    CO2
> > <NA> 2000  3  9 18  30 373.60
> > <NA> 2000  3 14 18  30 373.34
> > <NA> 2000  3 23 18   0 373.01
> >
> > I have tried every format option on the help page.  How can I read in
> > my decimal dates (e.g., 2000.18790)?
> >
> > Note that these data (CO2) are irregularly spaced in time (Time).
> >
> > Ultimately I would like to fit a trigonometric polynomial (first
> > harmonic) to these data in order to smooth them and obtain values
> > between measurements.  Any suggestions you can provide on how to do
> > this would be much appreciated.
> >
> > Thank you for your help.
> >
> > Sheri
> >
> > Sheri L. Conner Gausepohl
> > Graduate Research Assistant
> > Department of Atmospheric Science
> > Colorado State University
> 
> Try this:
> 
> library(its)
> dd <- read.table(myfile, header = TRUE)
> tt <- paste(dd$Y, "-", dd$M, "-", dd$D, " ", dd$H, ":", dd$Min, sep = "")
> co2 <- its(dd$CO2, as.POSIXct(tt))
> co2 # display co2
> 


or even easier use ISOdatetime:

library(its)
dd <- read.table(myfile, header = TRUE)
co2 <- with(dd, its(CO2, ISOdatetime(Y, M, D, H, Min, 0)))