

   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

        rs3(y,x1,x2,x3power=c(1,1,1),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

         x3: Third covariate

      power: Initial estimates of the three power transforma-
             tions

     weight: Weight vector

     family: glm family

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

        `rs3' fits a three-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', `rs2'.

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

        rs3(native,area,elevation,santacruz,p=c(-1,0.8,1),fam=poisson,weight=wt)

