replacement of coefficients in a polynomial by absolute values?



Hello,
 Given a polynomial p(x) = sum(a_j x^j) in which j = (j_1, . . . , j_n) 
is a multi-index,  is there a simple way to obtain the polynomial
                                q(x) = sum(abs(a_j) x^j)            ?

Following some previous discussion, one could first extract the 
coefficients, replace them by their absolute values, and then get q, but 
I wondered if there are some special tools to make this easier.

TIA,
 -sen