> I can't tell whether evaluating object$call$data in environment(object$formula) is a better or worse idea than parent.frame().
I have struggled with this a lot over the years. There is a bunch of wonky code in lme4, e.g. here <https://github.com/lme4/lme4/blob/master/R/lmer.R#L814-L838>, that tries to look for data in different possible locations, but I don't think anything works perfectly/robustly. https://stackoverflow.com/questions/14945274/determine-whether-evaluation-of-an-argument-will-fail-due-to-non-existence On Mon, Sep 23, 2024 at 3:54 PM Ivan Krylov via R-devel <r-devel@r-project.org> wrote: > > В Sun, 22 Sep 2024 10:23:50 -0400 > John Fox <j...@mcmaster.ca> пишет: > > > > Evaluating object$call$data in the environment of the suggested > > > nlme:::model.matrix.lme function may also not work right. Without an > > > explicit copy of the data, the best environment to evaluate it in > > > would be parent.frame(). > > > > I'm afraid that I don't understand the suggestion. Isn't > > parent.frame() the default for the envir argument of eval()? Do you > > mean the parent frame of the call to model.matrix.lme()? > > Yes, I do mean the parent frame of the model.matrix.lme() function > call. While eval()'s default for the 'envir' argument is > parent.frame(), this default value is evaluated in the context of the > eval() call. Letting model.matrix.lme() call eval() results in the > 'envir' being the eval()'s parent, the model.matrix.lme() call frame. > > In most cases, model.matrix.lme() works as intended: either lme() has > been given the 'data' argument, so object$data is not NULL and the > branch to eval() is not taken, or 'data' has not been given, so both > object$data and object$call$data are NULL, and NULL doesn't cause any > harm when evaluated in any environment. In the latter case > model.matrix.default() can access the variables in the environment of > the formula. > > With keep.data = FALSE, the function may evaluate object$call$data in > the wrong environment: > > maybe_model_matrix <- function(X) > model.matrix(lme(distance ~ Sex, random = ~ 1 | Subject, X, > contrasts=list(Sex=contr.sum), keep.data=FALSE)) > > maybe_model_matrix(Orthodont) > # Error in eval(object$call$data) : object 'X' not found > > ...but then model.matrix.default doesn't work on such objects either, > and if the user wanted the data to be accessible, they could have set > keep.data = TRUE. I can't tell whether evaluating object$call$data in > environment(object$formula) is a better or worse idea than > parent.frame(). > > -- > Best regards, > Ivan > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
