writing null space basis in MATLAB without using null(A)

My teacher wants us to find the basis of the null space of a function in MATLAB. This 开发者_运维百科is the exact question.

Use the MATLAB function rref and the function lead above to write a MATLAB function N=nullbase(A) which computes a matrix N whose columns form a basis for the nullspace of A. Your file nullbase.m should not use the MATLAB functions rank or null.

Please someone help me, thank you.

What you're looking for is the SVD (singular value decomposition). Because this sounds like a homework problem, I won't give away the whole answer, but this hint should help. MATLAB has an SVD function: http://www.mathworks.com/help/techdoc/ref/svd.html