[R] output data by date?

jim holtman
Wed, 28 Nov 2012 13:03:47 -0000

Your date "string" is sorted in alphabetic order.  You need to convert
to a Date class and then sort as this example shows:

> x <- c('10.5.2011', '11.21.2011', '4.5.2011',
'5.17.2011', '6.27.2011', '8.16.2011')
> # convert to Date
> xD <- as.Date(x, format = "%m.%d.%Y")
> # notice difference in ordering
> sort(x)
[1] "10.5.2011"  "11.21.2011" "4.5.2011"
"5.17.2011"  "6.27.2011"
"8.16.2011"
> sort(xD)
[1] "2011-04-05" "2011-05-17" "2011-06-27"
"2011-08-16" "2011-10-05"
"2011-11-21"
>


On Wed, Nov 28, 2012 at 7:13 AM, Kathleen Regan <kath.regan at gmail.com>
wrote:
> Dear Helpers,
>
> I have a dataset X, with no missing values, everything is in order, R reads
> it correctly, and I have already done some statistical analyses on the
> dataset. The data are in order by date (six sampling dates in one year,
> earliest to latest) and I now want to generate boxplots for each parameter
> for each date.
>
> However, R outputs the boxplots in some order that I do not understand (eg.
> 10.5.2011, 11.21.2011, 4.5.2011, 5.17.2011, 6.27.2011, 8.16.2011) instead
> of chronologically as the data are in the dataframe.
>
> I tried reformatting the date field from English (US) to German, just in
> case my R was confused, but still R seems to use its own rules. The data do
> not occur in any rank or order with R's way of organizing the dates
(not
> highest to lowest, or lowest to highest) so I don't know why it is
ordering
> the dates as it is.
>
> This also happened when I ran ANOVAs on the parameters. I got the same
> output (mean values and Tukey HSD significance) using the dates formatted
> in both ways (whew! I would have really been worried, otherwise!) But now
> for the boxplots, which might eventually be included in the paper, I want
> to make it easier for the reader to interpret, so would like to have them
> ordered from earliest (4.5.2011- April, to 11.21.2011 - November.)
>
> Does anyone have a suggestion for how I can correct this?
>
> Thanks very much and my apologies if this has been covered before. I looked
> before posting my question, however, and couldn't find anything.
>
> --
> Kathleen Regan
>
> University of Hohenheim
>
> Institute of Soil Science and Land Evaluation
>
> Soil Biology Section
>
> Emil-Wolff-Str. 27
>
> D-70593 Stuttgart-Hohenheim
>
> "Traveler, there is no road. We make the road by walking."
>
> phone: +49(0)711 459 23118
>
> fax: +49(0)711 459 23117
> E-mail:kath.regan at gmail.com
>
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>
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--
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.