# wbound

(Not recommended) Write boundary condition file

`wbound` is not recommended. Use `applyBoundaryCondition` instead.

## Syntax

``fid = wbound(b,filename)``

## Description

example

````fid = wbound(b,filename)` writes a boundary function, specified by the boundary condition matrix `b`, to a file with the name `filename.m`. ```

## Examples

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Create a 2-D geometry and specify boundary conditions in the PDE Modeler app, export them to the MATLAB® workspace, and then write the boundary conditions to a file.

Start the PDE Modeler app and draw a unit circle and a unit square.

```pdecirc(0,0,1) pderect([0 1 0 1])```

Enter `C1-SQ1` in the Set formula field.

Use the default Dirichlet boundary condition u = 0 for all boundaries. To verify the boundary condition, switch to boundary mode by selecting Boundary > Boundary Mode. Use Edit > Select all to select all boundaries. Select Boundary > Specify Boundary Conditions and verify that the boundary condition is the Dirichlet condition with `h = 1`, `r = 0`.

Export the geometry and the boundary conditions to the MATLAB workspace by selecting the Export Decomposed Geometry, Boundary Cond's option from the Boundary menu.

Decompose the exported geometry into minimal regions. The result is one minimal region with five edge segments: three circle edge segments and two line edge segments.

Write the resulting boundary condition matrix to a file. Name the file `boundary.m`.

`fid = wbound(b,"boundary");`

## Input Arguments

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Boundary conditions, specified as a boundary matrix. Typically, you export a boundary matrix from the PDE Modeler app.

Data Types: `double`

Geometry file name, specified as a string or a character vector.

Data Types: `char` | `string`

## Output Arguments

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File identifier, returned as an integer. If `wbound` cannot write the file, `fid` is `-1`. For more information about file identifiers, see `fopen`.