Re: [R] Error in plot.lm

From: peter dalgaard <>
Date: Fri, 11 Mar 2011 22:36:09 +0100

On Mar 11, 2011, at 20:31 , David Winsemius wrote:

> Are you sure you need I() on the LHS? The I function is designed to avoid the confusion related to the dual use of the arithmetic operator symbols affecting the construction of the model matrix, but I don't think that applies to the LHS of the formula.
> (See Dalgaard's comments if desiring higher authority.)

Dalgaard is somewhat amused at

(a) being elevated to god-like status
(b) his actual post starting "I don't think you need I() on the LHS, ..."

Anyways, Jeff knows very well that I() is unneeded, but he had issues with other LHS expressions. The I() problem goes away if you put it inside unclass(), which may be a workaround in other cases. Or, perhaps, plot.lm() really ought to do that internally.


Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email:  Priv:

______________________________________________ mailing list
PLEASE do read the posting guide
and provide commented, minimal, self-contained, reproducible code.
Received on Fri 11 Mar 2011 - 21:40:15 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Fri 11 Mar 2011 - 22:00:21 GMT.

Mailing list information is available at Please read the posting guide before posting to the list.

list of date sections of archive