On Oct 24, 2011, at 11:34 AM, Rich Shepard wrote:
On Fri, 21 Oct 2011, David Winsemius wrote:
The first thing I would try would be
with(subset(chemdata, param %in% c('TDS', 'Cond', 'Mg', 'SO4',
'Cl', 'Na', and 'Ca') , 1:4) ,
xtabs(quant ~ site + sampdate + param) )
David,
Need to remove the 'and' from the above.
Right. The perils of untested code, but then, you never provided any
data to test did you.
The results include _all_ params,
I doubt it. I suspect there are all zeroes in the tables for levels
which were not in that list of subset criteria.
not just the six above and all sampdates
from 31 years ago. The first table begins with
The appearance of levels with all zeroes is probably because I didn't
include drop.unused.levels = FALSE in the xtabs specification.
, , param = AGP
sampdate
site 1981-11-30 1982-04-28 1982-05-24 1982-06-29
1983-10-20
BC-0.5 0.000 0.000 0.000 0.000 0.000
BC-1 0.000 0.000 0.000 0.000 0.000
BC-1.5 0.000 0.000 0.000 0.000 0.000
BC-2 0.000 0.000 0.000 0.000 0.000
BC-3 0.000 0.000 0.000 0.000 0.000
and 20296 lines later (in emacs) that param ends and so does R's
[ reached
getOption("max.print") -- omitted 31 row(s) and 65 matrix slice(s) ].
It's always better to work with small subsets in developing your code.
Why didn't the '%in%' limit the output to the specified params?
Is the design of expressions such as the above based on your years of
experience with R or are such topics covered in a document somewhere?
I don't take your meaning here. Using `subset` to limit analyses to a
particular segment of data it pretty fundamental. `xtabs` is a fairly
standard operation. You could ahve broken them apart and created a
working subset first and then used it with xtabs.
I have
bought almost a dozen R books in the past few months, have read most
of
them, and don't recall seeing anything like the above.
Thanks,
Rich
--
David Winsemius, MD
West Hartford, CT
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