specials and ::

You are right of course, Peter, but I can see where some will get confused.?? In a formula
some symbols and functions are special operators, and others are simple functions.?? That
is the reason one needs I(events/time) to put a rate in as a variable.??? Someone who
types 'offset' at the command line will see that there actually IS a function behind the
scenes.

Does anyone see a downside to Bill Dunlap's suggestion where the first step of my formula
processing would be to "clean off" any survival:: modifiers???? That is, something that
will break? After all, the code already has a lot of? "if (....) "? lines for other common
user errors.?? I could view it as just saving me the time to deal with the 'we found an
error' emails.?? I would output the corrected version as the "call" component.

Terry

On 8/27/24 03:38, peter dalgaard wrote:

In my view, that's just plain wrong, because strata() is not a function but a special operator in a model formula. Wouldn't it also blow up on stats::offset()?

Oh, yes it would:

lm(y~x+offset(z))

Call:
lm(formula = y ~ x + offset(z))

Coefficients:
(Intercept)            x
       0.7350       0.0719

lm(y~x+stats::offset(z))

Call:
lm(formula = y ~ x + stats::offset(z))

Coefficients:
       (Intercept)                 x  stats::offset(z)
            0.6457            0.1078            0.8521


Or, to be facetious:

lm(y~base::"+"(x,z))

Call:
lm(formula = y ~ base::"+"(x, z))

Coefficients:
      (Intercept)  base::"+"(x, z)
           0.4516           0.4383



-pd

On 26 Aug 2024, at 16:42 , Therneau, Terry M., Ph.D. via R-devel<r-devel at r-project.org>  wrote:

The survival package makes significant use of the "specials" argument of terms(), before
calling model.frame; it is part of nearly every modeling function. The reason is that
strata argments simply have to be handled differently than other things on the right hand
side. Likewise for tt() and cluster(), though those are much less frequent.

I now get "bug reports" from the growing segment that believes one should put
packagename:: in front of every single instance.   For instance
        fit <- survival::survdiff( survival::Surv(time, status) ~ ph.karno +
survival::strata(inst),  data= survival::lung)

This fails to give the correct answer because it fools terms(formula, specials=
"strata").    I've stood firm in my response of "that's your bug, not mine", but I begin
to believe I am swimming uphill.   One person responded that it was company policy to
qualify everything.

I don't see an easy way to fix survival, and even if I did it would be a tremendous amout
of work.   What are other's thoughts?

Terry



-- 

Terry M Therneau, PhD
Department of Quantitative Health Sciences
Mayo Clinic
therneau at mayo.edu

"TERR-ree THUR-noh"

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