User`s manual

Examples of C MEX-Files

2-21

Handling Complex Data

Complex data from MATLAB is separated into real and imaginary parts.

MATLAB’s API provides two functions,

mxGetPr and mxGetPi, that return

pointers (of type

double *) to the real and imaginary parts of your data.

This example takes two complex row vectors and convolves them.

/* $Revision: 1.8 $ */

/*=========================================================

* convec.c

* Example for illustrating how to pass complex data

* from MATLAB to C and back again

* Convolves two complex input vectors.

* This is a MEX-file for MATLAB.

*=======================================================*/

#include "mex.h"

/* Computational subroutine */

void convec( double *xr, double *xi, int nx,

double *yr, double *yi, int ny,

double *zr, double *zi)

{

int i,j;

zr[0] = 0.0;

zi[0] = 0.0;

/* Perform the convolution of the complex vectors. */

for(i = 0; i < nx; i++) {

for(j = 0; j < ny; j++) {

*(zr+i+j) = *(zr+i+j) + *(xr+i) * *(yr+j) - *(xi+i)

* *(yi+j);

*(zi+i+j) = *(zi+i+j) + *(xr+i) * *(yi+j) + *(xi+i)

* *(yr+j);

}