I think you could bit that using (inside your function) something like
this
old.o <- options(na.action = na.fail)
# old.o <- options(na.action = na.pass)
on.exit(old.o)
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Rolf Turner" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, June 02, 2005 4:14 PM
Subject: [R] Caution on the use of model.matrix.
I have just been bitten by a quirk in the behaviour of model.matrix.
I used model.matrix inside a function, and passed to it a formula
that was built elsewhere.
The formula was of the form ``y ~ x + w + z''. Now, model.matrix
cheerfully accepts formulae of this form, although it only
***needs*** the right hand side, i.e. ``~ x + w + z'' --- the ``y''
can be dropped (but in general needn't be).
The quirk by which I was bitten was that if the y column of the data
frame being used contains missing values, then the corresponding
rows
are dropped (silently) and the resulting design matrix has rows
corresponding only to the non-missing values of y. This was not the
desired behaviour in my application.
Might I respectfully suggest to R Core that a WARNING be added to
the
help for model.matrix to the effect that
model.matrix(y~x + w + z,XXX)
and
model.matrix(~x + w + z,XXX)
give DIFFERENT results if the column ``y'' of the data frame XXX
contains missing values?
cheers,
Rolf Turner
[EMAIL PROTECTED]
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