https://au.mathworks.com/help/matlab/apiref/mxsetn.html
mxSetN (C) - Set number of columns in mxArray - MATLAB
mxSetN sets the number of columns in the specified mxArray.
csetnumbermatlab
https://www.mathworks.com/help/matlab/apiref/mxsetn_fortran.html
mxSetN (Fortran) - Set number of columns in mxArray - MATLAB
mxSetN sets the number of columns in the specified mxArray.
fortransetnumbercolumnsmatlab