tree, istree (Robust Control Toolbox)

Robust Control Toolbox

tree, istree

Pack all information and data from several matrices, vectors and/or strings into a single `tree' variable. tree implements the Robust Control Toolbox hierarchical tree data structure.

Syntax

T = tree(nm,b1,b2,,bn) 
[i] = istree(T) 
[i,b] = istree(T,path)

Description
tree creates a data structure T, called a tree containing several variables and their names. This single variable contains all the data and dimension information from its branches b1, b2, b3,, bn along with a numerical index and a string name for each branch.

The input argument nm is a string containing a list of names (separated by commas) to be assigned to the respective branches b1,b2,...,bn

```
 nm = 'name1,name2,name3,,nameN';
```

The names may be any valid variable names and must be separated by commas. If no names are to be assigned, set "nm = ";.

The input arguments b1,b2,,bn (called the root branches of the tree) may be matrices, vectors, strings, or even trees themselves, thus enabling the creation of a hierarchical tree data structure within the MATLAB framework.

istree checks whether a variable T is a tree or not.

```
 I = istree(T);
```

returns I=1 (true) if "T" is a tree variable created by the function tree; otherwise it returns I=0 (false). When the second input argument PATH is present, the function istree checks the existence of the branch specified by PATH. For example,

```
 [I,B] = istree(T,PATH);
```

returns "I = 1", if both "T" is a tree variable and "PATH" is a valid path to a branch in the tree T. Otherwise, it returns "I = 0". If the optional output argument "B" is present, then B returns the value of the branch specified by PATH, provided T is a tree and PATH is a valid path in T.

Related functions include the following:

branch: returns branches of a tree. 
branch(T,0): returns nm, the list of branch names. 
T(1): returns the number N of the root branches.

Examples
A hierarchical tree structure shown inFigure 1-17 can be built as follows

tree1 = tree('a,b,c',a,b,c); 
tree3 = tree('w,x',w,x); 
tree2 = tree('tree3,y,z',tree3,y,z); 
bigtree = tree('tree1,tree2',tree1,tree2);

Figure 1-17: Example of Tree Structure.

To extract a variable from a tree, simply use the branch function:

[tree1,tree2] = branch(bigtree); 
% getting variable w: 
w = branch(bigtree,'tree2/tree3/w'); 
% getting several variables: 
[w,b] = branch(bigtree,'tree2/tree3/w,tree1/b');

Paths in a tree are also determined by the numerical indices of the branches which lead to the branch of interest. For example, the last line above is equivalent to

```
 [w,b] = branch(bigtree,'2/1/1,1/2');
```

See branch for further details.

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