Fit model to a new response.
This is normally an internal function, but it can be overloaded to extend simr to other packages.
doFit(y, fit, subset, ...)
y: new values for the response variable (vector or matrix depending on the model).fit: a previously fitted model object.subset: boolean vector specifying how much of the data to use. If missing, the model is fit to all the data. This argument needs to be implemented for powerCurve to work....: additional options.a fitted model object.