[R] summary table newbie question

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From: Jeff D. Hamann (jeff.hamann@forestinformatics.com)
Date: Thu 13 May 2004 - 02:41:24 EST


Message-id: <000d01c4383f$fa2e9b30$0c00a8c0@rodan>

I've got a newbie question and I got a little lost in the "table helps".
I've got a data.frame I would like to summarize as a (and pardon for the
lack of correct vernacular) data collection matrix. My data looks like,

   stand siteindex age acres pct.acres
1 232 116 45 8477.3105 0.56159458
2 234 121 25 11120.1530 0.73667441
3 235 132 25 5399.4605 0.35769691
4 236 115 5 6308.3969 0.41791103
5 240 116 45 473.1533 0.03134489
6 241 116 15 21790.9595 1.44358105
7 245 171 25 686.9867 0.04551066
8 246 134 25 15176.8082 1.00541478
9 247 99 35 1754.9282 0.11625835
10 251 125 55 7396.1098 0.48996851
...blah, blah, blah...

and when I attempt to create a summary table using aggregate, I get the
following results,

> aggregate( stands$acres, by=list(stands$age,stands$siteindex), sum )

    Group.1 Group.2 x
1 95 86 6403.5457
2 5 88 1517.6781
3 45 88 3555.3213
4 125 89 6269.2633
5 95 90 3154.3531
6 55 93 14006.9781
7 15 94 98.9918
8 35 94 2241.0531
9 105 94 431.0281

but what I really want is a matrix where the rows and columns are classes
(in increments of 5 or 10 or whatever) and the cells are the sums (or means
or whatever) for the data.frame. I guess it would be equivalent to like
surf.ls/surf.gls without fitting a trend but that would also allow me to
plot the results graphically in addition to simply printing out the table
using xtable.

Jeff.

---
Jeff D. Hamann
Forest Informatics, Inc.
PO Box 1421
Corvallis, Oregon USA 97339-1421
541-754-1428
jeff.hamann@forestinformatics.com
www.forestinformatics.com

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