engdemo.c

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/* $Revision: 1.8.4.4 $ */
/*
 *      engdemo.c
 *
 *      A simple program to illustrate how to call MATLAB
 *      Engine functions from a C program.
 *
 * Copyright 1984-2011 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 };

        /*
         * Call engOpen with a NULL string. This starts a MATLAB process
     * on the current host using the command "matlab".
         */
        if (!(ep = engOpen(""))) {
                fprintf(stderr, "\nCan't start MATLAB engine !!!\n");
                return EXIT_FAILURE;
        }

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

        /*
         * Create a variable for the 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 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 figure.
         */
        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.
             */
            printf("%s", buffer);

            /*
             * 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;
}