Class: Tree

A Tree object allows accessing individual trees (>4m height) in iLand via Javascript.

Note that using Javascript with individual trees can be slow.

Accessing a tree

Trees can be accessed via the Management object or TreeList list within ABE. The Management object provides tree() and treeObject() functions. Similarly, the TreeList includes tree() and treeObject().

Reference vs object

iLand provides two distinct ways to access trees, namely as reference (to an internal object) or as a Javascript object. Access via reference is faster, but tree references can not be used for later access. See the example:

// load all trees of resource unit 0:
management.loadResourceUnit(0);
// access via reference: every call to the tree() functions modifies the reference:
var t1=management.tree(0); // the first tree (dbh=10)
var t2=management.tree(1); // the second tree (dbh=20)
console.log("Tree1: " + t1.dbh + ", Tree2: " + t2.dbh); // -> yields "Tree1: 20, Tree2: 20"!!!!

// access via object:
var t1=management.treeObject(0); // the first tree (dbh=10)
var t2=management.treeObject(1); // the second tree (dbh=20)
console.log("Tree1: " + t1.dbh + ", Tree2: " + t2.dbh); // -> yields "Tree1: 10, Tree2: 20"

// References are, however, useful for iterating over a list of trees:
var sum_dbh=0;
for (var i=0;i<management.count;++i)
    sum_dbh += management.tree(i).dbh;
console.log("Mean dbh: " + sum_dbh / management.count);

Properties Overview

Name	Type	Description
`dbh`	`double`	The dbh (diamter at breast height), in cm.
`flags`	`int`	`flags` is a binary encoded set of tree flags (see https://iland-model.org/outputs#Tree_Removed_Output for a list of all flags).
`species`	`string`	The species (4-character species ID), e.g. ‘piab’.
`valid`	`bool`	`false` if the tree object is not valid, `true` otherwise.
`x`	`double`	The x-coordinate of the tree, in m.
`y`	`double`	The y-coordinate of the tree, in m.

Methods Overview

Method	Return Type	Description
`expr(expression)`	`double`	`expr()` can be used to retrieve the value of an iLand expression iland-model.org/Expression. All tree variables can be accessed via the expression. Note that
`flag(aflag)`	`void`	`flag` returns true or false for the given `aflag` for the current tree.
`info()`	`string`	A string with memory address, Id, dbh, height, and coordinates of the tree.
`setFlag(aflag, value)`	`void`	The function sets the the flag `aflag` to the provided value.

Properties Details

`dbh`

double

The dbh (diamter at breast height), in cm.

`flags`

int

flags is a binary encoded set of tree flags (see https://iland-model.org/outputs#Tree_Removed_Output for a list of all flags).

`species`

string

The species (4-character species ID), e.g. ‘piab’.

`valid`

bool

false if the tree object is not valid, true otherwise.

`x`

double

The x-coordinate of the tree, in m.

`y`

double

The y-coordinate of the tree, in m.

Methods Details

`expr(expression)`

Returns: double

expr() can be used to retrieve the value of an iLand expression iland-model.org/Expression. All tree variables can be accessed via the expression. Note that the expression is a string and can contain mathematical operations and a set of pre-defined functions.

`flag(aflag)`

Returns: void

flag returns true or false for the given aflag for the current tree.

Parameters:

aflag (Flags): the flag to check

`info()`

Returns: string

A string with memory address, Id, dbh, height, and coordinates of the tree.

Return Value Description: A human-readable string with key characteristics of the tree.

`setFlag(aflag, value)`

Returns: void

The function sets the the flag aflag to the provided value. Note that not all flags are setable. Possible values are currently: TreeAffectedBite and TreeNoHarvest.

Parameters:

aflag (Flags): the flag to check
value (bool): value to set the flag, defaults to true

Example:

for (let i=0;i<stand.trees.count;++i)
      if( i % 17 == 0) {
        let t = stand.trees.tree(i);
        t.setFlag(Tree.TreeNoHarvest);
      }