[R] Sorting Posix Data

[Prof Brian Ripley]

On Mon, 26 Nov 2001, Shawn Way wrote:

> I have a fairly large set of data with the following attributes:
>
> >str(raw.data)
> `data.frame':	1429 obs. of  16 variables:
>  $ TStamp       :`POSIXlt', format: chr  "2001-11-25 02:00:00" "2001-11-25
> 01:55:00" "2001-11-25 01:50:00" "2001-11-25 01:45:00" ...
>  $ iPDT.AHU14.14: num  0.0122 0.0125 0.0120 0.0120 0.0122 ...
>  $ iPDT.AHU14.15: num  0.0121 0.0123 0.0119 0.0119 0.0121 ...
>  $ iPDT.AHU14.16: num  0.00635 0.00657 0.00608 0.00608 0.00631 ...
>  $ iPDT.AHU14.17: num  0.0300 0.0304 0.0302 0.0300 0.0303 ...
>  $ iPDT.AHU15.15: num  0.0986 0.0984 0.0980 0.0979 0.0983 ...
>  $ iPDT.AHU15.16: num  0.0510 0.0521 0.0502 0.0507 0.0513 ...
>  $ iPDT.AHU15.17: num  0.0665 0.0692 0.0683 0.0686 0.0674 ...
>  $ PDT.AHU16.15 : num  0.0741 0.0753 0.0760 0.0747 0.0738 ...
>  $ PDT.AHU16.16A: num  0.00152 0.00235 0.00167 0.00191 0.00172 ...
>  $ PDT.AHU16.16B: num  0.0556 0.0563 0.0570 0.0560 0.0558 ...
>  $ PDT.AHU16.17 : num  0.00883 0.00937 0.00877 0.00869 0.00873 ...
>  $ PDT.AHU16.18 : num  0.141 0.142 0.142 0.144 0.141 ...
>  $ PDT.AHU16.19 : num  0.0120 0.0123 0.0117 0.0116 0.0119 ...
>  $ PDT.AHU16.20A: num  8.55e-06 1.55e-05 0.00e+00 2.36e-07 1.92e-06 ...
>  $ PDT.AHU16.20B: num  0.0532 0.0536 0.0534 0.0532 0.0535 ...
> >
>
> Unfortunately, the data is in the reverse order based on the date TStamp. Is
> there any fairly easy method for reordering this set of data byt the first
> column, a PosiX Date?

o <- sort(as.POSIXct(raw.data$TStamp))
raw.data[o, ]

or if you really just want to reverse the order

raw.data[nrow(raw.data):1, ]

>
>
> "Don't rush me, you rush a miracle, you get a rotten miracle."
> -Miracle Max, The Princess Bride
>
>
> Shawn Way
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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