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A class wrapper for Matlab(c) ActiveX Control

, 21 Oct 2002
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Eases up the use of the Matlab(c) COM server...
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Sample Image - matlabengine.png

Introduction

Matlab(c) is a well-known scientific software covering a wide range of engineering and mathematicals fields. It contains also a set of complete and powerfull visualization tools.

Matlab(c) contains it's own language and you can easily develop applications on it. However, sometimes you will want to run it from a C/C++ application and that's where everything get's tricky. In fact, although Matlab(c) comes with a C API, it is complicated to use: linking problems, compiler special flags and other mysterious bugs (maybe I did it all wrong).

Another solution is to use the COM interface of the ActiveX control. The sad thing about this interface is that... it's COM and you end up with dozens of lines of code... That's where the CMatlabEngine gets in the play. It hides all the COM code (getting CLSID, getting IDispatch, allocating variants, setting function arguments and many others) and enables you to focus on the main part of the job: use Matlab(c).

This article will discuss the main features the class, for further details check the Doxygen documentation that is shipped with the demo project. Note that you can also generate it by running Doxygen on MatlabEngine.h

Initializing the engine

All the initialization code is contained in the constructor of CMatlabEngine. You can check that the server has been correctly initialized by calling IsInitialized:

// Initializing COM
CoInitialize(NULL);

...
// Hooking matlab engine
CMatlabEngine mt;
if (!mt.IsInitialized())
   // could not initialize matlab engine, do something about it

Do not forget to uninitialize COM when quitting the application:

CoUninitialize();

Engine main methods

The matlab engine contains 5 main methods: Execute, PutMatrix, GetMatrix, PutString and GetString

Executing Matlab(c) code:

You can execute Matlab(c) code by calling Execute( LPCTSTR szMatlabCode ):

// this code will show the classic Matlab(c) demo
mt.Execute(_T("surf(peaks)"));
mt.Execute(_T("title('demo')"));

Sending arrays to Matlab(c)

You can send array, real or complex, in the form of vector to Matlab(c) by using PutMatrix.Note that the vector in PutMatrix have to be ordered line by lines: for a matrix M of size (mxn), M(i,j) is equivalent to M[i* n + j].

UINT nRows=10; // number of rows
UINT nCols=2;  // number of columns
vector<double> v( nRows * nCols );
// filling up v
...
// sending v to Matlab(c) with name "Mv"
mt.PutMatrix( _T("M"), v, nRows, nCols);
// M is now a matrix in the Matlab(c) workspace

Retreiving arrays from matlab

You can retreive arrays (real or complex) by calling GetMatrix( It is the dual of PutMatrix):

mt.Execute(_T("v=[1 2 3; 4 5 6]';"));
vector<double> vReal;
UINT nRows, nCols;
mt.GetMatrix(_T("v"), nRows, nCols, vReal);	

nRows and nCols now contains the dimension of the array and vReal the data.

Sending string to Matlab(c)

Piece of cake using PutString:

   mt.PutString("text", "Inserting a string named text");

Getting string from Matlab(c)

Use the method GetString:

LPTSTR szText;
// we suppose that myText is a string variable in Matlab
mt.GetString("myText",szText);
Note that szText is allocated on the heap by GetString, the memory cleaning is left to the user.

Workspace

You can modify the workspace you are working on by using SetWorkspace. By default, the workspace is "base". If you want to declare global variables, use "global" workspace.

Handling the Matlab Window state

  • Minimize the command window,
    mt.MinimizeWindow();
    
  • Maximize the command window,
    mt.MaximizeWindow();
    
  • Show, hide the command window,
    mt.Show( true /* true to make it visible, false to hide it*/);
    
  • Get the visibility state the command window,
    if(mt.IsVisivle())
        // Matlab is server is visible...
    
  • Quit the command window,
    mt.Quit();
    

Known bugs and limitations

Matlab 5.3 and earlier

Some function interface from the Matlab engine have been introduced only with the version 6.0 therefore user with version earlier than 6.0 would have faced problem with the class.

If you have a Matlab earlier than v6.0, undefine the MATLAB_VERSION_6 constant that is at the beginning of MatlabEngine.h, it will disable the following functions: IsVisible, Show, PutString, GetString

Further developments

  • Write PutCellArray and GetCellArray to write and read cell arrays.

Reference and further reading

Revision History

21-10-2002Added references
10-09-2002
  • GetString is now working! At last !
  • Fixed bugs in GetResult, GetMatrix thanks to Juan Carlos Cobas.
09-25-2002
  • GetMatrix is now working! At last !
09-23-2002
  • Added PutString method
  • Added MATLAB_VERSION_6 string for Matlab version < 6. Thanks for ZHANG Yan for finding the workaround.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Jonathan de Halleux
Engineer
United States United States
Jonathan de Halleux is Civil Engineer in Applied Mathematics. He finished his PhD in 2004 in the rainy country of Belgium. After 2 years in the Common Language Runtime (i.e. .net), he is now working at Microsoft Research on Pex (http://research.microsoft.com/pex).

Comments and Discussions

 
QuestionThanks Pinmembergongjinnan31-May-12 16:40 
Generaldisp('hello'); Pinmemberxtlan16-Sep-09 13:07 
GeneralRe: disp('hello'); Pinmemberxtlan18-Sep-09 11:58 
GeneralPutMatrix() doesn't WORK Pinmember53rg1003-Oct-07 0:26 
Generalfor superNoobs Pinmemberfdfszfsfds23-Apr-07 5:53 
GeneralFirst time PinmemberOvat1-Aug-06 12:12 
Questionmatlab 7 support? Pinmemberarnonm11-Jun-05 21:28 
AnswerRe: matlab 7 support? Pinmemberarnonm11-Jun-05 22:13 
GeneralRe: matlab 7 support? Pinmemberrdiaz329-Nov-05 0:13 
GeneralRe: matlab 7 support? PinmemberAndy Kuo21-Apr-06 11:06 
GeneralRe: matlab 7 support? Pinmemberrdrouin29-May-06 4:09 
GeneralGetMatrix \ SetMatrix Pinmemberg_briner@hotmail.com30-Dec-04 23:48 
Generalmatlab error Pinmemberergter16-Dec-03 22:55 
GeneralRe: matlab error PinmemberJonathan de Halleux17-Dec-03 1:20 
Generalmatlab error Pinmemberiryweiuo16-Dec-03 18:50 
GeneralRe: matlab error PinmemberJonathan de Halleux16-Dec-03 21:22 
Generalsimple questions Pinmemberastridwahlin15-Dec-03 4:44 
GeneralRe: simple questions PinmemberJonathan de Halleux16-Dec-03 21:20 
QuestionNot releasing memory? Pinmemberarnonm4-Jun-03 1:22 
AnswerRe: Not releasing memory? My unvalidated solution Pinmemberarnonm4-Jun-03 2:06 
GeneralRe: Not releasing memory? My unvalidated solution PinmemberJonathan de Halleux4-Jun-03 3:20 
GeneralBug in CMatlabEngine::ErrHandler Pinmemberarnonm26-May-03 3:44 
GeneralRe: Bug in CMatlabEngine::ErrHandler Pinmemberarnonm26-May-03 21:14 
GeneralGood fix PinmemberJonathan de Halleux26-May-03 22:06 
Thank you for the fix. I'll post an update of the source but it will take time to get to CP.

 
Jonathan de Halleux.

GeneralThanks! Pinmemberarnonm22-May-03 0:39 

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