[R] Formatting YYYY-MM after reading text file [RESOLVED]

[MacQueen, Don]

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-bounces at r-project.org on behalf of rshepard at 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
>
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