[Boost-users] ublas and matrix expression

I have an expression a = (X^T * X)^-1 * X^T * y where x is an n * k matrix and y is an n row vector How do I implement this expression in ublas? I can create and populate the matrices and can do the product of matrices and the transpose use prod and trans, but I'm unsure on the ^-1. Can I do this with ublas? (I don't know much about matrices, but have been given the above expression as a way of finding a polynomial fit for a set of data). Thanks in advance Russell