[R] Formatting YYYY-MM after reading text file

[David Barron]

as.yearmon(allchem$sampdate)

worked for me.

David

On 26 June 2015 at 19:44, Rich Shepard <rshepard at appl-ecosys.com> wrote:
>   Data file 'example.dat' has this format:
>
> stream,sampdate,param,quant
> B,1992-03,Cl,4
> B,1992-03,SO4,33
> B,1992-03,pH,8.43
> B,1992-04,Cl,4
> B,1992-04,SO4,32
> B,1992-04,pH,8.46
> B,1992-05,Cl,4
> B,1992-05,SO4,31
> B,1992-05,pH,8.43
>
>   It's read into R with
> allchem <- read.table('example.dat', stringsAsFactors=F, header=T, sep=',')
>
> and yields this structure:
>
> str(allchem)
> 'data.frame':   2226 obs. of  4 variables:
>  $ stream  : chr  "B" "B" "B" "B" ...
>  $ sampdate: chr  "1992-03" "1992-03" "1992-03" "1992-04" ...
>  $ param   : chr  "Cl" "SO4" "pH" "Cl" ...
>  $ quant   : num  4 33 8.43 4 32 8.46 4 31 8.43 6 ...
>
>   Because the date field contains year and month but no day, as.Date() does
> not work. ?as.Date displays the help file for yearmon in package 'zoo.'
> Reading this lead me to try:
>
> allchem$sampdate <- as.yearmon(format(%Y-%m))allchem$sampdate
>
> which produces the error, Error: unexpected SPECIAL in "allchem$sampdate <-
> as.yearmon(format(%Y-%".
>
>   I do not see the proper syntax to change the sampdate char string to
> year-month dates. Advice appreciated.
>
> Rich
>
> ______________________________________________
> R-help at 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.