On Aug 11, 2010, at 6:45 PM, Charles C. Berry wrote:
On Wed, 11 Aug 2010, David Winsemius wrote:
On Aug 11, 2010, at 6:03 PM, Jarrett Byrnes wrote:
I have formulae with coefficents that I would like to update.
However, I get some strange results. For example, see the
following:
For the formula y ~ d+ 3*r+t
Did you really get meaningful results from that formula? Care to
provide an example? Maybe there is something more for me to learn.
I want to add a variable p, so
> update(y~d+0*r+t, .~.+p)
In formulas the "*" operator is an interaction creator. so you told
R to make 0 + r + 0:r. Probably not what you thought you were
doing. So what were you trying to do anyway?
produces
y ~ d + t + p - 1
Which at least explains why you got the -1 (which in R formulas is
that same as +0).
If the coefficient is not 0, but rather, something else - say, 3,
What do you think you are accomplishing when you put a scalar
coefficient in the formula?
Maybe he wants
?I
Possibly, but wouldn't that just result in a "deflation" by a factor
of 3 of the estimated coefficient if you wrappedI around that rem ...
I(3*r) ? I also wondered if he might need to be referred to:
?offset
??
?? back 'atcha.
--
David.
Chuck
I get the following:
> update(y~d+3*r+t, .~.+p)
Error in terms.formula(tmp, simplify = TRUE) :
invalid model formula in ExtractVars
> Is there a way to do this,
or a different call I should be trying?
What you should be doing depends on what you want to happen.
--
David
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
