 <p>You could write your own method, using the code for other packages' methods as a template. </p> <p>But in the short term, it's probably a lot easier to grab the coefficient values from your <code>m.2</code> object. <code>m.2$coefficients</code> contains all the fitting coefficients, labelled as to which term they belong to. You'll then have to write a little function to match the algebraic form of your <code>PIV~(X3*X1)+(X3*X2)+X3+X1+X2+X4+X5</code> formula, with those coefficients applied.</p>