I believe that I have a basic understanding of zoo and how to use read.zoo on a text file, What I have not seen in the zoo help files and vignettes is how to convert a data frame to a zoo matrix for irregular time series analyses.
An example data frame is structured like this: str(burns.cast) 'data.frame': 256 obs. of 47 variables: $ site : Factor w/ 143 levels "BC-0.5","BC-1",..: 1 1 1 2 2 2 2 2 2 2 $ sampdate : Date, format: "1996-04-19" "1996-05-21" ... $ Ca : num 76.6 NA NA NA NA ... $ Cond : num 712 403 731 NA NA NA NA NA NA NA ... $ HCO3 : num 162 152 212 NA NA NA NA NA NA NA ... $ SO4 : num 175 57 194 NA NA NA NA NA NA NA ... $ TDS : num 460 212 530 NA NA NA NA NA NA NA ... ... What I think I need is a matrix that orders sampdate, has the numeric values for TDS, and retains the factor of site (so that I can compare TDS values on a given date by site). The August 2011 version of zoo docs suggests that I need to modify the above from a data frame to a matrix, but there is more than a single class involved. Would something like this work? z <- zoo(burns.cast$TDS, order.by = burns.cast$sampdate, style = vertical) And where do I include the site factor? A pointer to docs or an example will be much appreciated. Rich ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
