code: def linear(self, fnct, x, y, sd=None, wt=1.0, fid=0):
          
          self._fit(fitfunc="linear", fnct=fnct, x=x, y=y, sd=sd, wt=wt, fid=fid)
docs: Make a linear least squares solution.
  
          Makes a linear least squares solution for the points through the
          ordinates at the x values, using the specified fnct. The x can be of
          any dimension, depending on the number of arguments needed in the
          functional evaluation. The values should be given in the order:
          x0[1], x0[2], ..., x1[1], ..., xn[m] if there are n observations,
          and m arguments. x should be a vector of m*n length; y (the
          observations) a vector of length n.
  
          :param fnct: the functional to fit
          :param x: the abscissa values
          :param y: the ordinate values
          :param sd: standard deviation of equations (one or more values used
                     cyclically)
          :param wt: an optional alternate for `sd`
          :param fid: the id of the sub-fitter (numerical)