Data extraction from MATLAB to mex-function setup

Hi all,

I am trying to extract data calculated in the MATLAB environment into the mex-function set-up in vain. Could someone please point out the error in my code or anything that I am doing wrong?

int *aidx, *idx;
const mxArray *m_sort[2], *m_pctemp[3];

../* Necessary initializations for 'sort' is made and all is well so far */..

    mexCallMATLAB(2, m_sort, 3, &m_pctemp, "sort"); // Works fine

    /* Displays the correct data in 'm_sort' */
    mexCallMATLAB(0, NULL, 1, &m_sort[0], "disp"); //(double)  
    mexCallMATLAB(0, NULL, 1, &m_sort[1], "disp"); //(int) 

    aidx = (int *)mxGetData(m_sort[1]);
OR
    aidx = mxGetPr(m_sort[1]);

    idx = ivector(0, 23); // memory allocation with indices range(0-23)
  for (i = 1; i <= 24; i++) // Matlab indices is from 1 to 24
    idx[i-1] = aidx[i]; // Wrong values from aidx[] here

I will need the array m_sort[1] that holds the indices for further processing. It looks like I am not extracting the values properly. Both the APIs fail to give me the correct values.

I believe using mxGetData with proper casting (int *) is the right way to get the integer data from m_sort[1].

Am I right? If not, Please tell me what is the right way to do it? or if I should provide more information to get me off this problem.

Thanks in advance.

Answer 1

[Jan]

The sorting index is a DOUBLE vector in Matlab. Therefore you need:

int *idx;
double *aidx;
aidx = mxGetPr(m_sort[1]);
...
   idx[i-1] = (int) aidx[i];

[Rajaram B S R]

Thank you , Jan.

How to know the return type of the vectors? The documentation does not mention anything about it.

[Kaustubha Govind]

You can use mxGetClassID or mxGetClassName to find the type of the mxArray.

[Jan]

@Rajaram: Of course the documentation explains this. It might be hard to find without using the mathcing keywords.

The type of the *returned* arrays is defined inside the Mex file. The type of the input arrays can be checked by rge commands Kaustubha has mentioned already, and by mxIsDouble, mxIsSingle etc.

[Rajaram B S R]

Thank you, Kaustubha and Jan.