basal.area {CTFS} | R Documentation

## Basal Area by Categories (User defined groups)

### Description

Computes basal area (m^2) for all trees or any user defined categorization of trees. If a tree has more than one stem, the other stems recorded in the multi-stem file are included in its basal area, if the file exists. Two datasets are used: one with the primary stem and one with all multiple stems for that cenus. The two datasets contain completely non-overlapping sets of DBH. Adding the two together produces the total basal area for each tagged tree.

### Usage

    basal.area(census1, mult1, alivecode = c("A"), mindbh = 10,
            split1 = NULL, split2 = NULL)

### Arguments

`census1` | name of census datafile for first census, must be a dataframe
`mult1` | name of file (not in quotes) must be a dataframe with trees as rows and column as DBH. Tree tag numbers can appear multiple times in this file if there is more than two stems for a tree.
`alivecode` | character, codes of the variable `status` that indicate the tree is alive and has a valid DBH. The default is: "A" for trees >= 10 mm DBH
`mindbh` | minimum DBH to determine which trees will be included in computation
`split1` | a vector of categorical values of the same length as `datafile` which groups trees into classes of interest for which growth values are computed. This vector can be composed of charcters or numbers.
`split2` | a second vector of categorical values of the same length as `datafile` which groups trees into classes of interest for which growth values are computed. This vector can be composed of charcters or numbers.

### Details

See `CTFS.basalarea` for details on the computation methods of basal area and associated functions.

A tree is included for the computation based on its value for `status` and `dbh` for a single census.

### Value

`basal.area` returns a list of arrays with the following named components. Values for each category of the split vectors are provided.

`$basalarea` | sum of basal area m^2
`$meandate` | mean date of enumeration

If the vector(s) `split1` and `split2` are provided by the user, then basal area and associated statistics are computed for each value of the vectors. The vectors are nested so that basal area is computed for each category of `split2` within each category of `split1`

### Author(s)

Rick Condit, Suzanne Lao, Pamela Hall

### See Also

`CTFS.basalarea`

### Examples

    ## Not run:
    1. Default use of basal.area
    basal.out <- basal.area(tst.bci90.full, tst.bci90.mult)

    2. Basal area for trees >= 100 mm (10 cm)
    basal100.out <- basal.area(tst.bci90.full, tst.bci90.mult, mindbh=100)

    3.  Basal area for each species
    spp.vct <- tst.bci90.full$sp
    basal.spp.out <- basal.area(tst.bci90.full, tst.bci90.mult,
    split1=spp.vct)
    ## End(Not run)

[Package CTFS version 1.00 Index]