

   FFiitt aa TTwwoo--ffaaccttoorr BBooxx--TTiiddwweellll NNoonnlliinneeaarr RReessppoonnssee SSuurrffaaccee

        rs2(y,x1,x2,power=c(1,1),weight=rep(1,length(y)),family=normal)

   AArrgguummeennttss::

          y: Response variable

         x1: First covariate

         x2: Second covariate

      power: Initial estimates of the two power transformations

     weight: Weight vector

     family: glm family

   DDeessccrriippttiioonn::

        `rs2' fits a two-covariate power-transformed response
        surface by iterating the function, `glm'.

   VVaalluuee::

        A list of class, rs, is returned containing the model
        and the power estimates.

   SSeeee AAllssoo::

        `lm', `glm', `gnlr', `gnlr3', `fmr', `rs3'.

   EExxaammpplleess::

        rs2(native,area,elevation,fam=poisson,weight=wt)

