MATLAB Engine API

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• Download demo project - 9.5 Kb

Introduction

In two past articles (Solving Engineering Problems Using MATLAB C API and Solving Engineering Problems Using MATLAB C++ Math Library), I show you how can a programmer develop an application that using MATLAB features like computing complex engineering problems. But if you are not familiar with MATLAB APIs or MATLAB C++ interface or these are hard coding techniques, this article is for you.

MATLAB Engine

MATLAB provides some API functions for controlling it. These APIs required that you installed MATLAB on your target machine. We named these APIs, MATLAB Engine API. For an alternative method, you can use MATLAB ActiveX control. For more information refer to article: A class wrapper for Matlab (C) ActiveX Control by Jonathan de Halleux.

Using MATLAB Engine

For using MATLAB engine, you must follow these steps:

1. Add matlab.h interface file to stdafx.h or any desired interface/implementation file.
2. Add MATLAB libraries to your project. For this reason, we need these libraries: libeng.lib, libmx.lib, libmatlb.lib, libmat.lib, libmmfile.lib.
3. Add MatlabEng.h and MatlabEng.cpp files to your project.
4. Declare a variable with type of CMatlabEng. (Remember to include MatlabEng.h interface file).
5. Use member functions of CMatlabEng class, to control MATLAB and send commands to it and retrieve computed values or plotted graphs!
6. Compile your project.

CMatlabEng

Following codes are definition of CMatlabEng class. It's very simple to use.

class CMatlabEng {
public:
    int OutputBuffer(char *p, int n);
    void OpenSingleUse(const char *startcmd, void *dcom, int *retstatus); 
    int GetVisible(bool* value); 
    int SetVisible(bool value); mxArray* GetVariable(const char* name); 
    int PutVariable(const char *name, const mxArray *mp); 
    int EvalString(const char* string);
    void Open(const char* StartCmd); int Close(); CMatlabEng();
    virtual ~CMatlabEng();
    
protected:
    Engine* pEng;
}; 

CMatlabEng in detail

Table 1 is a complete reference of member functions of CMatlabEng class.

Sample Program

Following program is a sample that uses CMatlabEng class. Program logic is very simple.

#include "stdafx.h"

#include "MatlabEng.h"


#define message(x) printf(x"\n\n")

int main(int argc, char* argv[])
{
    CMatlabEng matlab;
    
    //open new matlab session

    message("Starting MATLAB");
    matlab.Open(NULL);

    message("Hiding MATLAB");
    matlab.SetVisible(FALSE);
    message("Press any key to continue");
    getch();

    message("Showing MATLAB");
    matlab.SetVisible(TRUE);
    message("Press any key to continue");
    getch();
    
    mxArray *T = NULL;
    double time[10] = { 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 };

    //create matrix

    T = mxCreateDoubleMatrix(1, 10, mxREAL);
    memcpy((void *)mxGetPr(T), (void *)time, sizeof(time));
    
    //send matrix T to matlab

    message("Send matrix T to matlab");
    matlab.PutVariable("T", T);

    //Evaluate matlab command

    matlab.EvalString("D = .5.*(-9.8).*T.^2;");

    //Plot results

    message("Plot(T, D)");
    matlab.EvalString("plot(T,D);");    
    matlab.EvalString("title('Position vs. Time for a falling object');");
    matlab.EvalString("xlabel('Time (seconds)');");
    matlab.EvalString("ylabel('Position (meters)');");
    matlab.EvalString("grid;");

    //pause to see results

    message("Press any key to continue");
    getch();
    
    //destroy matrix

    mxDestroyArray(T);
    
    //show MATLAB graphics capabilities

    message("Showing MATLAB graphics capabilities");
    matlab.EvalString("z=peaks(25);");
    matlab.EvalString("surf(z);");
    matlab.EvalString("colormap(jet);");
    matlab.EvalString("knot;");

    //pause

    getch();

    //close session

    matlab.Close();

    return 0;
}