model: Object of class dat; switches on this argument.
group: list of vector pairs (x2 index, dataset index) for which the part of the residual vector is to be determined
multimodel: Object of class multimodel
thetalist: Object of class multitheta
clpindepX: Object of class matrix containing the matrix determined directly by the nonlinear parameters (e.g., a concentration matrix in the case of a kinetic model) in the case that this matrix does not depend on the x2 index
finished: logical determining whether fitting is finished that triggers the storage of results
returnX: logical determining whether to just return the matrix X directly dependent on nonlinear parameters; this is used in the finite difference derivative of X used to get standard error estimates on the conditionally linear parameters.
rawtheta: numeric vector of nonlinear parameters to be optimized by nls; this is used in the finite difference derivative of X used to get standard error estimates on the conditionally linear parameters.