A number of these are going to be written as built-in facilities, with no .m code available from Mathworks. You should consider looking in places like the Matlab File Exchange, or google, for the appropriate code. In some cases you might find C code to do the work, and you may have to write a MEX wrapper to interface between Matlab and the external code.
Be sure to test the resulting code -- different implementations of the same algorithm can end up with different results, whether due just to round-off error or other reasons. Or due perhaps to the code assuming row-order instead of column order.
