On Feb 3, 2011, at 1:05 PM, Graves, Gregory wrote:
Yes, as far as I can tell, "sampling.date" is a character vector of
the format "1/15/2008". It resides in the leftmost column of the
tapply output.
"station.code" are the A, B, C column headers which refer actual
water quality station locations, and the values below those headers
correspond to the "sampling.date" when samples were taken. Actually
what I have done is to take the mid-point of each month and
calculated its mean to deal with multiple samples taken in one
month, and to generate NAs where no sample was taken by purposefully
not adding the na.rm=T to the tapply command.
Normally I would do this:
rdate<-as.POSIXct(strptime(date,format="%m/%d/%Y")) #convert
sampling.date to date R can handle
plot(A~rdate)
If I just submit station.code like
A
I get all the values for "Station A".
It is in converting the sampling.date to an "rdate" that has me
stumped. One reason being that in the tapply output the character
vector representing date has no column name. I can't access that
column.
It looks like a zoo object. "zoo" objects hold their time values in
the rownames attribute. But since its not really ordered properly, it
may just be a table with rownames. The str() function applied to the
object from tapply would tell you the answer.
--
David.
Gregory A. Graves, Lead Scientist
Everglades REstoration COoordination and VERification (RECOVER)
Wetland Watershed Sciences / Restoration Sciences Department
South Florida Water Management District
Phones: DESK: 561 / 682 - 2429
CELL: 561 / 719 - 8157
-----Original Message-----
From: David Winsemius [mailto:dwinsem...@comcast.net]
Sent: Thursday, February 03, 2011 12:50 PM
To: Graves, Gregory
Cc: r-help@r-project.org; Goodman, Patricia; Gorman, Patricia
Subject: Re: [R] tapply output as a dataframe
On Feb 3, 2011, at 11:29 AM, Graves, Gregory wrote:
My tapply output is generated as follows:
a=tapply(value,list(sampling.date,station.code),mean)
Why not give us sampling.date (which is probably NOT really a date but
rather a character vector) and station.code so we can show you how to
create a more appropriate structure?
which gives me this (in part):
A B C D E F G H I
J K
1/15/2008 0.004 0.027 0.019 0.015 0.035 0.022 0.007 0.038 0.042
0.045 0.0350
1/15/2009 0.027 0.027 0.031 0.015 0.008 0.021 0.007 0.027 0.026
0.029 0.0210
1/15/2010 0.016 0.020 0.015 0.022 0.015 0.013 0.007 0.014 0.019
0.019 0.0180
10/15/2007 0.052 0.051 0.032 0.024 0.017 0.044 0.015 0.058 0.063
0.061 0.0640
10/15/2008 0.042 0.054 0.030 0.017 0.024 0.030 0.019 0.044 0.047
0.051 0.0390
10/15/2009 0.047 0.035 0.031 0.020 0.012 0.039 0.019 0.051 0.055
0.054 0.0350
The only way I can figure out how to resolve this, such that I can,
for example, plot station "A" against date, is to export the tapply
output as a csv, and then reimport.
Suggestions? I couldn't find a solution to this likely SIMPLE
problem
Perhaps. but we haven't really been told what the problem is, have we?
in Crawley or multiple searches of R help.
Gregory A. Graves, Lead Scientist
David Winsemius, MD
West Hartford, CT
David Winsemius, MD
West Hartford, CT
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