I am currently writing a MEX function that will have to work with a cell array in MATLAB. The MEX file is written in C.

Essentially, the input to my function will be a cell array where each entry is a numeric matrix with real values. A simple example is: 

 C = cell(1,2);
C{1} = ones(10,10);
C{2} = zeros(10,4);

I would like to be able to access the numeric arrays C{1} and C{2} in my MEX file. Ideally, I would like to do this without having to create a second copy of the data in my MEX File (i.e. get pointers for them).

Using the previous example, my current approach is as follows: 

/* declare a pointer variable to the incoming cell array after it is passed to the MEX function */
mxArray C_CELL = (mxArray *) mxGetData(prhs[0]) 

/* declare  a 2 x 1 array of pointers to access the cell array in C */
double *myarray[2] //

/* point towards the contents of C_CELL */
myarray[0] = mxGetPr(C_CELL[0])
myarray[1] = mxGetPr(C_CELL[1]) 

Unfortunately this seems to yield "invalid use of undefined type 'struct mxArray_tag'" errors. 

Answers: 

You need to use mxGetCell to extract the contents of a cell array. 

 mxArray *cellArray[2];
cellArray[0] = mxGetCell(prhs[0], 0);
cellArray[1] = mxGetCell(prhs[0], 1);