code: def I_minus_R(self,singular_value):
          
          if self.__I_R is not None and singular_value == self.__I_R_sv:
              return self.__I_R
          else:
              if singular_value > self.jco.ncol:
                  return self.parcov.zero
              else:
                  #v2 = self.qhalfx.v[:, singular_value:]
                  v2 = self.xtqx.v[:, singular_value:]
                  self.__I_R = v2 * v2.T
                  self.__I_R_sv = singular_value
                  return self.__I_R
docs: get I - R at singular value
  
          Parameters
          ----------
          singular_value : int
              singular value to calc R at
  
          Returns
          -------
          I - R : pyemu.Matrix
              identity matrix minus resolution matrix at singular_value