The class Combined1 defines the the residual error variance according
to the formula g(sigma_inter, sigma_slope, c_error, f(x, theta)) = sigma_inter + sigma_slope*f(x,theta)).
Combined1 objects are typically created by calls to Combined1 and contain the following slots that are herited from
the class Combined1c:
.Object:An object of the Class Combined1
sigma_inter:A numeric value giving the sigma inter of the error model.
sigma_slope:A numeric value giving the sigma slope of the error model.