output data by date?

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)

sort(xD)

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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