[R] data.frame subset?

[Jeff D. Hamann]

Can someone tell me why this is since I can't seem to find an explination in
the docs or FAQ for this.

Since there are no "BM" in the mtrs data.frame, but only in the "parent"
data.frame (trees), I'm assuming the subset data.frame is still associated
with the original. Is that correct and how would I create a completly
separate data.frame since I'll be using by, lapply and such on the subset
data.frame using "sp" which currently causes by to choke...

> mtrs <- trees[trees$m == 1,]
> mtrs
    plot tree sp m dbh tht   bfvol   cfvol
1      1    1 DF 1  44 185 3825.79  622.97
2      1    2 DF 1  38 188 3166.69  504.12
26     3    1 DF 1  42 185 3568.80  578.09
51     5    4 DF 1  30 189 2071.36  348.28
67     7    1 DF 1  33 168 2036.30  342.90
70     7    4 DF 1  45 180 3665.82  621.90
71     7    5 DF 1  30 160 1530.88  274.69
81     9    1 DF 1  44 175 3398.52  576.79
82     9    2 DF 1  68 205 9516.82 1461.21
95    11    1 DF 1  30 170 1775.60  299.54
96    11    2 DF 1  44 197 4249.98  680.64
97    11    3 DF 1  44 187 3914.88  632.42
107   11   13 WH 1  44 175 3398.52  576.79
121   13    2 WF 1  48 205 5241.14  827.57
126   13    7 DF 1  40 182 3188.77  522.43
138   15    2 DF 1  69 182 7852.22 1285.42
143   15    7 DF 1  28 142 1146.77  207.67
159   17    9 DF 1  12  88   99.13   25.43
177   19    7 DF 1  37 162 2309.06  391.48
> attributes( mtrs$sp )
$class
[1] "factor"

$levels
[1] "BM" "DF" "WF" "WH"

>

---
Jeff D. Hamann
Forest Informatics, Inc.
PO Box 1421
Corvallis, Oregon USA 97339-1421
(office) 541-754-1428
(cell) 541-740-5988
jeff.hamann at forestinformatics.com
www.forestinformatics.com