MATLAB: How to create a structure inside structure in mex file.

creating nested structure using mex functionmexno_details

[EDIT: 20110512 23:27 CDT – clarify – WDR]

I have a binary tree from which I want to create a structure.

Best Answer

I think what you intend to construct is a nested structure. Try something like:

#include "mex.h"
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
 {
  char* level1_fnames[] = {"level1_a", "level1_b"};
  char* level2_fnames[] = {"level2_a1", "level2_a2"};
  mxArray* level2_struct;
  plhs[0] = mxCreateStructMatrix(1, 1, 2, level1_fnames);
  level2_struct = mxCreateStructMatrix(1, 1, 2, level2_fnames);
  mxSetField(plhs[0], 0, "level1_a", level2_struct);
}

Related Solutions

MATLAB: Building Mex file with Fortan

Your main problem is that you need to create the output array PLHS(1) before you access it. Also your NLHS and NRHS types are wrong. Try this:

#include <fintrf.h>
C
C Gateway routine
C
    SUBROUTINE MEXFUNCTION(NLHS, PLHS, NRHS, PRHS)
    implicit none
C mexFunction arguments:
    MWPOINTER PLHS(*), PRHS(*)
    INTEGER NLHS, NRHS
    mwPointer, external :: mxGetPr, mxGetPi
    mwPointer, external :: mxCreateDoubleMatrix, mxCreateNumericArray
    mwSize, external :: mxGetM, mxGetN
    MWPOINTER YPP 
    mwSize M, N
    integer*4 ComplexFlag
    REAL *8 RYPP(1)
    RYPP(1) = 10
    M = 1
    N = 1
    ComplexFlag = 0
    PLHS(1) = mxCreateDoubleMatrix( M, N, ComplexFlag )
    YPP = MXGETPR(PLHS(1))
    CALL MXCOPYREAL8TOPTR(RYPP, YPP, M*N)
    RETURN
    END

MATLAB: How to place a matrix of unsigned characters into a field in a MATLAB structure

To receive a matrix of unsigned characters into a field in a MATLAB structure, you can use our C API routines. These routines will copy the unsigned character matrix into the field of the MATLAB structure. The logical structure of an MATLAB structure is illustrated below:

 mxArray *(structure) #created using mxCreateStructureMatrix
     |
     |
       -- mxArray *(field1)  #created using mxCreate#####
     |
     |
      -- mxArray *(field2)  #created using mxCreate#####
     |
     |
      -- mxArray *(field3)  #created using mxCreate#####

An unsigned char is equivalent to an unsigned 8-bit integer, which you can create in your MEX-file using the mxCreateNumericArray routine:

field3 = mxCreateNumericMatrix(20, 2, mxUINT8_CLASS, mxREAL);
//The above says to create a real (as opposed to complex) 20 x 2 matrix of type "uint8".

You can now add this to the structure that was previously created with the mxCreateStructMatrix using the mxSetField routine.

 mxArray *structure;
 mxArray *field3;
 unsigned char *pdata;
 structure = mxCreateStructMatrix(1, 1, 3, {"field1", "field2","field3"});
 mxSetField(structure, 0, "field1", mxCreateDoubleScalar(20));
 mxSetField(structure, 0, "field2", mxCreateDoubleScalar(2));
 field3 = mxCreateNumericMatrix(20, 2, mxUINT8_CLASS, mxREAL);
 //returns the pointer to the data part of the MATLAB array
 pdata = mxGetData(field3);
 // Now copy actual data into the data part of field3
 for (int j = 0 ; j < 2 ; j++) {
    for (int i = 0 ; i < 20 ; i++) {
          pdata[20*j + i] = CppMatrix[i][j];
    }
 }
 mxSetField(structure, 0,"field3", field3);

Best Answer

Related Solutions

MATLAB: Building Mex file with Fortan

MATLAB: How to place a matrix of unsigned characters into a field in a MATLAB structure

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