From Setzer.Woodrow@epamail.epa.gov  Fri Jun  1 15:23:03 2001
From: Setzer.Woodrow@epamail.epa.gov (Setzer.Woodrow@epamail.epa.gov)
Date: Fri, 01 Jun 2001 10:23:03 -0400
Subject: [Rd] formulas in variables in modeling functions
Message-ID: <OFC33AA95D.63C7CD15-ON85256A5E.004E396D@rtp.epa.gov>

I first noticed this in gnls, but it also happens in lm, so I suspect the
following phenomenon is universal in modeling functions.  Modify the
example from the lm help:

model <- as.formula(weight ~ group)
lm(model)

The result will be printed:

> lm(model)

Call:
lm(formula = model)
^^^^^^^^^^^^^^^^^
Coefficients:
(Intercept)     groupTrt
      5.032       -0.371

This is because in lm, (where the return value is z) z$call is set to cl,
and cl <- match.call().

My question is:  would it break things to add the line

cl[["formula"]] <- formula
after
cl <- match.call()
?

The result of this is:

> lm.new(model)

Call:
lm.new(formula = weight ~ group)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Coefficients:
(Intercept)     groupTrt
      5.032       -0.371

R. Woodrow Setzer, Jr.                                            Phone:
(919) 541-0128
Experimental Toxicology Division                       Fax:  (919) 541-5394
Pharmacokinetics Branch
NHEERL MD-74; US EPA; RTP, NC 27711

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[Rd] formulas in variables in modeling functions
Setzer.Woodrow@epamail.epa.gov