core/matlab/examples/eng_mat/engdemo.c

/* $Revision: 1.1 $ */
/*
 *  engdemo.c
 *
 *  This is a simple program that illustrates how to call the MATLAB
 *  Engine functions from a C program.
 *
 * Copyright 1984-2003 The MathWorks, Inc.
 * All rights reserved
 */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "engine.h"
#define  BUFSIZE 256

int main()

{
    Engine *ep;
    mxArray *T = NULL, *result = NULL;
    char buffer[BUFSIZE+1];
    double time[10] = { 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 };

    /*
     * Start the MATLAB engine locally by executing the string
     * "matlab"
     *
     * To start the session on a remote host, use the name of
     * the host as the string rather than \0
     *
     * For more complicated cases, use any string with whitespace,
     * and that string will be executed literally to start MATLAB
     */
    if (!(ep = engOpen("\0"))) {
        fprintf(stderr, "\nCan't start MATLAB engine\n");
        return EXIT_FAILURE;
    }

    /*
     * PART I
     *
     * For the first half of this demonstration, we will send data
     * to MATLAB, analyze the data, and plot the result.
     */

    /* 
     * Create a variable for our data
     */
    T = mxCreateDoubleMatrix(1, 10, mxREAL);
    memcpy((void *)mxGetPr(T), (void *)time, sizeof(time));
    /*
     * Place the variable T into the MATLAB workspace
     */
    engPutVariable(ep, "T", T);

    /*
     * Evaluate a function of time, distance = (1/2)g.*t.^2
     * (g is the acceleration due to gravity)
     */
    engEvalString(ep, "D = .5.*(-9.8).*T.^2;");

    /*
     * Plot the result
     */
    engEvalString(ep, "plot(T,D);");
    engEvalString(ep, "title('Position vs. Time for a falling object');");
    engEvalString(ep, "xlabel('Time (seconds)');");
    engEvalString(ep, "ylabel('Position (meters)');");

    /*
     * use fgetc() to make sure that we pause long enough to be
     * able to see the plot
     */
    printf("Hit return to continue\n\n");
    fgetc(stdin);
    /*
     * We're done for Part I! Free memory, close MATLAB engine.
     */
    printf("Done for Part I.\n");
    mxDestroyArray(T);
    engEvalString(ep, "close;");


    /*
     * PART II
     *
     * For the second half of this demonstration, we will request
     * a MATLAB string, which should define a variable X.  MATLAB
     * will evaluate the string and create the variable.  We
     * will then recover the variable, and determine its type.
     */
      
    /*
     * Use engOutputBuffer to capture MATLAB output, so we can
     * echo it back.  Ensure first that the buffer is always NULL
     * terminated.
     */

    buffer[BUFSIZE] = '\0';
    engOutputBuffer(ep, buffer, BUFSIZE);
    while (result == NULL) {
        char str[BUFSIZE+1];
        /*
         * Get a string input from the user
         */
        printf("Enter a MATLAB command to evaluate.  This command should\n");
        printf("create a variable X.  This program will then determine\n");
        printf("what kind of variable you created.\n");
        printf("For example: X = 1:5\n");
        printf(">> ");

        fgets(str, BUFSIZE, stdin);
      
        /*
         * Evaluate input with engEvalString
         */
        engEvalString(ep, str);
        
        /*
         * Echo the output from the command.  First two characters are
         * always the double prompt (>>).
         */
        printf("%s", buffer+2);
        
        /*
         * Get result of computation
         */
        printf("\nRetrieving X...\n");
        if ((result = engGetVariable(ep,"X")) == NULL)
          printf("Oops! You didn't create a variable X.\n\n");
        else {
        printf("X is class %s\t\n", mxGetClassName(result));
        }
    }

    /*
     * We're done! Free memory, close MATLAB engine and exit.
     */
    printf("Done!\n");
    mxDestroyArray(result);
    engClose(ep);
    
    return EXIT_SUCCESS;
}

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GridLAB-D^TM Version 1.0

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