I would have just assigned them all to the first day of the month, using as.Date( paste0(allchem$sampdate,'-01') ) (or maybe the middle of the month represented by the 15th) and then had a variable that was of the Date class in the base R (with which I am familiar, no small consideration).
Depending on what needs to be done with them -- plotting with a date axis? -- calculating elapsed time between sampling events? -- I suppose one or the other of 'yearmon' or 'Date' might be more convenient. -Don -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 6/26/15, 12:04 PM, "R-help on behalf of Rich Shepard" <r-help-boun...@r-project.org on behalf of rshep...@appl-ecosys.com> wrote: >On Fri, 26 Jun 2015, Rich Shepard wrote: > >> allchem$sampdate <- as.yearmon(format(%Y-%m))allchem$sampdate > > Reading the yearmon help page again led me to try > allchem$sampdate <- as.yearmon(allchem$sampdate) >which produces the following structure: > >'data.frame': 2226 obs. of 4 variables: > $ stream : chr "B" "B" "B" "B" ... > $ sampdate:Class 'yearmon' num [1:2226] 1992 1992 1992 1992 1992 ... > $ param : chr "Cl" "SO4" "pH" "Cl" ... > $ quant : num 4 33 8.43 4 32 8.46 4 31 8.43 6 ... > >which appears to do what's needed: > >allchem > stream sampdate param quant >1 B Mar 1992 Cl 4.000 >2 B Mar 1992 SO4 33.000 >3 B Mar 1992 pH 8.430 >4 B Apr 1992 Cl 4.000 >5 B Apr 1992 SO4 32.000 >6 B Apr 1992 pH 8.460 >7 B May 1992 Cl 4.000 >8 B May 1992 SO4 31.000 >9 B May 1992 pH 8.430 >10 B Jun 1992 Cl 6.000 > > Not having before worked with dates like this I'll soon see what >happens >as the analyses proceed. > >Rich > >______________________________________________ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >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. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
