Learn more about MATLAB Builder NE

Passing Variable Arguments

Note   This example is similar to Simple Plot Example, except that the MATLAB function to be encapsulated takes a variable number of arguments instead of just one.

The purpose of the example is to show you the following:

• How to use the builder to convert a MATLAB function, drawgraph, which takes a variable number of arguments, to a method of a .NET class (Plotter) and wrap the class in a .NET component (VarArgComp). The drawgraph function (which can be called as a method of the Plotter class) displays a plot of the input parameters.

• How to access the component in a C# application (VarArgApp.cs) by instantiating the Plotter class and using MWArray to represent data.

  Note   For complete reference information about the MWArray class hierarchy, see the MWArray Class Library Reference (available online only).

• How to build and run the VarArgDemoApp application, using the Visual Studio .NET development environment.

Step-by-Step Procedure

1. If you have not already done so, copy the files for this example as follows:

   1. Copy the following folder that ships with the MATLAB product to your work folder:

      matlabroot\toolbox\dotnetbuilder\Examples\VS8\NET\VarArgExample
      

   2. At the MATLAB command prompt, cd to the new VarArgExample subfolder in your work folder.

2. Write the MATLAB functions as you would any MATLAB function.

   The code for the functions in this example is as follows:

    drawgraph.m

   function [xyCoords] = DrawGraph(colorSpec, varargin)
   ...
       numVarArgIn= length(varargin);
       xyCoords= zeros(numVarArgIn, 2);
   
       for idx = 1:numVarArgIn
           xCoord = varargin{idx}(1);
           yCoord = varargin{idx}(2);
           
           x(idx) = xCoord;
           y(idx) = yCoord;
           
           xyCoords(idx,1) = xCoord;
           xyCoords(idx,2) = yCoord;
       end
       
       xmin = min(0, min(x));
       ymin = min(0, min(y));
   
       axis([xmin fix(max(x))+3 ymin fix(max(y))+3])
       
       plot(x, y, 'color', colorSpec);
   
    
   

    extractcoords.m

   function [varargout] = ExtractCoords(coords)
   %EXTRACTCOORDS Extracts a variable number of two element x and y 
   % coordinate vectors from a two column array 
   %   [VARARGOUT] = EXTRACTCOORDS(COORDS) Extracts x,y coordinates 
   $   from a two column array
   %   This file is used as an example for the .NET Builder
   %   Language product.
    
   %   Copyright 2001-2003 The MathWorks, Inc.
   %   $Revision: 1.1.4.49 $  $Date$
   
       for idx = 1:nargout
           varargout{idx}= coords(idx,:);
       end
   

   This code is already in your work folder in /VarArgExample/VarArgComp/.

3. While in MATLAB, issue the following command to open the Deployment Tool dialog box:

   deploytool

4. Build the .NET component. See the instructions in Building Your Component for more details. Use the following information:

   Project Name	VarArgComp
   Class Name	Plotter
   File to compile	extractcoords.m

5. Write source code for an application that accesses the component.

   The sample application for this example is in VarArgExample\VarArgCSApp\VarArgApp.cs.

   The program listing is shown here.

    VarArgApp.cs

   // *******************************************************************************
   //
   //VarArgApp.cs
   //
   // This example demonstrates how to use MATLAB Builder NE to build a component
   // with a variable number of input and output arguments.
   //
   // Copyright 2001-2008 The MathWorks, Inc.
   //
   // *******************************************************************************
   
   using System;
   
   using MathWorks.MATLAB.NET.Utility;
   using MathWorks.MATLAB.NET.Arrays;
   
   using VarArgComp;
   
   
   namespace MathWorks.Examples.VarArgApp
    {
     /// <summary>
     /// This application demonstrates how to call components having methods with varargin/vargout arguments.
     /// </summary>
     class VarArgApp
       {
         #region MAIN
   
         /// <summary>
         /// The main entry point for the application.
         /// </summary>
         [STAThread]
         static void Main(string[] args)
           {
             // Initialize the input data
             MWNumericArray colorSpec= new double[]{0.9, 0.0, 0.0};
             MWNumericArray data= new MWNumericArray(new int[,]{{1,2},{2,4},{3,6},{4,8},{5,10}});  
             MWArray[] coords= null;
   
             try
               {
                 // Create a new plotter object
                 Plotter plotter= new Plotter();
   
                 //Extract a variable number of two element x and y coordinate vectors from the data array
                 coords= plotter.extractcoords(5, data);
   
                 // Draw a graph using the specified color to connect the variable number of input coordinates.
                 // Return a two column data array containing the input coordinates.
                 data= (MWNumericArray)plotter.drawgraph(colorSpec, coords[0], coords[1], coords[2],coords[3], coords[4]);
   
                 Console.WriteLine("result=\n{0}", data);
   
                 Console.ReadLine();  // Wait for user to exit application
   
                 // Note: You can also pass in the coordinate array directly.
                 data= (MWNumericArray)plotter.drawgraph(colorSpec, coords);
   
                 Console.WriteLine("result=\n{0}", data); 
    
                 Console.ReadLine();  // Wait for user to exit application
               }
   
             catch(Exception exception)
               {
                 Console.WriteLine("Error: {0}", exception);
               }
           }
   
         #endregion
       }
     }
   

   The program does the following:

   • Initializes three arrays (colorSpec, data, and coords) using the MWArray class library

   • Creates a Plotter object

   • Calls the extracoords and drawgraph methods

   • Uses MWNumericArray to represent the data needed by the methods

   • Uses a try-catch block to catch and handle any exceptions

   The following statements are alternative ways to call the drawgraph method:

   data= (MWNumericArray)plotter.drawgraph(colorSpec, 
                   coords[0], coords[1], coords[2],coords[3], coords[4]);
   ...
   data= (MWNumericArray)plotter.drawgraph((MWArray)colorSpec, coords);
   

6. Build the VarArgApp application using Visual Studio .NET.

   1. The VarArgCSApp folder contains a Visual Studio .NET project file for this example. Open the project in Visual Studio .NET by double-clicking VarArgCSApp.csproj in Windows Explorer. You can also open it from the MATLAB desktop by right-clicking VarArgCSApp.csproj > Open Outside MATLAB.

   2. Add a reference to the MWArray component, which is matlabroot\toolbox\dotnetbuilder\bin\architecture\framework_version
      \mwarray.dll.

   3. Add or, if necessary, fix the location of a reference to the VarArgComp component which you built in a previous step. (The component, VarArgComp.dll, is in the \VarArgExample\VarArgComp\x86\v2.0\debug\distrib subfolder of your work area.)

7. Build and run the application in Visual Studio .NET.

Simple Plot Example

Spectral Analysis Example

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