MATLAB Application Program Interface Reference

Get an mxArray's real data elements

#include "matrix.h"
double *mxGetPr(const mxArray *array_ptr);

Arguments

array_ptr

Pointer to an mxArray.

Returns

The address of the first element of the real data. Returns NULL if there is no real data.

Description

Call mxGetPr to determine the starting address of the real data in the mxArray that array_ptr points to. Once you have the starting address, it is fairly easy to access any other element in the mxArray.

Examples

Consider a MEX-file named DispReal that displays the value of every real element in the input mxArray

#include "mex.h"

void
mexFunction(int nlhs,mxArray *plhs[],int nrhs,const mxArray 
*prhs[])
{
 int    c, total_num_of_elements; 
 double *real_data_ptr;
  
   if (mxIsDouble(prhs[0]))  { 
     /* Get starting address of real data in input array. */
       real_data_ptr = (double *)mxGetPr(prhs[0]);

     /* Using pointer auto-increment, display every element in 
        the array. */
       total_num_of_elements = mxGetM(prhs[0]) * mxGetN(prhs[0]);
     
     /* Display the contents of every real value. */
       for (c = 0; c < total_num_of_elements; c++)
          mexPrintf("%g\n", *real_data_ptr++);
   } 
   else
      mexErrMsgTxt("First argument must be a double array.");
}

In MATLAB, create Values:

>> Values = [2 3; 5 7]
Values =
2     3
5     7

Pass Values as an argument to DispReal

>> DispReal(Values)
2
5
3
7

For additional examples, see mxGetPr.c and mxGetPr2.c in the mx subdirectory of the examples directory.