Hello,
I'm a complete newbie to R. Spent this past weekend reading The Art of R
Programming, The R Cookbook, the language spec, Wikis and FAQs. I sort-of have
my head around R; the dizzying selection of libraries, packages, etc? Not
really. I've probably missed or failed to understand something...
I have very a simple data set. Two years (ish) of temperature data, collected
and time-stamped every 10 minutes. Sample of the data from read.csv(...):
> head(temp.data)
DateTime Temperature
1 2009-11-23 23:20:00 62.9
2 2009-11-23 23:30:00 63.4
3 2009-11-23 23:40:00 63.6
4 2009-11-23 23:50:00 64.2
5 2009-11-24 00:00:00 64.5
6 2009-11-24 00:10:00 64.7
Converted to an xts object:
> str(temp_data)
xts [1:83089, 1] 62.9 63.4 63.6 64.2 64.5 64.7 65.2 65.3 65.8 65.6 ...
- attr(*, "index")= atomic [1:83089] 1.26e+09 1.26e+09 1.26e+09 1.26e+09
1.26e+09 ...
..- attr(*, "tzone")= chr ""
..- attr(*, "tclass")= chr [1:2] "POSIXct" "POSIXt"
- attr(*, "class")= chr [1:2] "xts" "zoo"
- attr(*, ".indexCLASS")= chr [1:2] "POSIXct" "POSIXt"
- attr(*, ".indexTZ")= chr ""
So far so good! I can do all kinds of cool things like plot individual months:
plot(temp_data["2009-12"]) and plot monthly, weekly, daily mean, sd, etc. (I
have to say, xts has been a dream to work with!)
What I would like to do is plot several sections of this data on the same graph.
Specifically, I would like to plot all the data from one calendar month,
regardless of year, on one plot.
i.e. one line for Jan 2009, another line for Jan 2010, anothe line for Jan
2011, etc.
I can use xts functions to slice the data into months (or weeks, or days), but
I am not sure how to arrange to get the X-axis to work right. If I do:
plot(temp_data["2010-01"]); lines(temp_data("2011-01"))
lines aren't overlayed; the output from lines() is lost because it is far off
of the right of the plot as the plot autoranged() the x and y axes. But I don't
think xlim is my problem so much as I need a way to 'slide'
temp_data["2011-01"] so that it will appear in the same part of the graph/plot
as the 2010-01 data does.
What I think I want to do is write a "normalizing" function that takes data for
any given month and makes it "year-free"??? This way I could plot corresponding
months on the same graph. One month, or a quarter, or even a full year. I don't
know, however, how to convince xts to ignore the year, or if there is an xts
compatible object that is year-free (or month-free for looking at week/day
segements)...
Pointers to online answers, google search terms, etc. greatly appreciated!
Thanks,
-=Doug
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