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Handle Complex Data in C MEX File

The exampleconvec.ctakes two complex row vectors and convolves them. The MEX file uses functions in the C Matrix API.

Create Source File

The following statements document the MEX function.

/*========================================================= * convec.c * example for passing complex data from MATLAB to C and back again * * convolves two complex input vectors * * This is a MEX-file for MATLAB. * Copyright 1984-2017 The MathWorks, Inc. *=======================================================*/

Create Gateway Routine and Verify Input and Output Parameters

The following statements add the C/C++ header filemex.hand creates themexFunctionentry point.

#include "mex.h" /* The gateway routine. */ void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[] ) { return; }

The following statements validate the number of parameters.

/* check for the proper number of arguments */ if(nrhs != 2) mexErrMsgIdAndTxt( "MATLAB:convec:invalidNumInputs", "Two inputs required."); if(nlhs > 1) mexErrMsgIdAndTxt( "MATLAB:convec:maxlhs", "Too many output arguments.");

The following statement verifies that the input arguments are row vectors.

/*Check that both inputs are row vectors*/ if( mxGetM(prhs[0]) != 1 || mxGetM(prhs[1]) != 1 ) mexErrMsgIdAndTxt( "MATLAB:convec:inputsNotVectors", "Both inputs must be row vectors.");

The following statement verifies that the input arguments are complex.

/* Check that both inputs are complex*/ if( !mxIsComplex(prhs[0]) || !mxIsComplex(prhs[1]) ) mexErrMsgIdAndTxt( "MATLAB:convec:inputsNotComplex", "Inputs must be complex.\n");

Create OutputmxArray

The following statements define the parameters for creating the outputmxArray.

size_t rows, cols; size_t nx, ny; /* get the length of each input vector */ nx = mxGetN(prhs[0]); ny = mxGetN(prhs[1]); rows = 1; cols = nx + ny - 1;

The following statement creates an array and sets the output pointerplhs[0]to it.

plhs[0] = mxCreateDoubleMatrix( (mwSize)rows, (mwSize)cols, mxCOMPLEX);

Create Computational Routine

The following statements defineconvec, the computational routine.

空白convec (mxArray * x, mxArray * y, mxArray * z,size_t nx, size_t ny) { mwSize i,j; /* get pointers to the complex arrays */ mxComplexDouble * xc = mxGetComplexDoubles(x); mxComplexDouble * yc = mxGetComplexDoubles(y); mxComplexDouble * zc = mxGetComplexDoubles(z); zc[0].real = 0; zc[0].imag = 0; /* perform the convolution of the complex vectors */ for(i=0; i

Callconvec

The following statement calls the computational routine.

convec(prhs[0], prhs[1], plhs[0], nx, ny);

Build and Test

At the MATLAB®command prompt type:

mex-R2018aconvec.c

Test the MEX file.

x = [3.000 - 1.000i, 4.000 + 2.000i, 7.000 - 3.000i]; y = [8.000 - 6.000i, 12.000 + 16.000i, 40.000 - 42.000i]; z = convec(x,y)
z = 1.0e+02 * Columns 1 through 4 0.1800 - 0.2600i 0.9600 + 0.2800i 1.3200 - 1.4400i 3.7600 - 0.1200i Column 5 1.5400 - 4.1400i

Compare the results with the built-in MATLAB functionconv.

conv(x,y)

See Also

Related Topics