Please do not post with ambiguous questions lacking sufficient R code
and data to represent the problem.
On Jul 7, 2010, at 4:41 PM, Bond, Stephen wrote:
Please, do not post if you do not know the answer. People will see
this has answers and skip.
More likely people will see that it has insufficient detail to
answer ,,, and then also skip. You still have not provided any insight
into the structure of "fixw".
I tried with
mat1=contrasts(fixw$snconv)
mat1=mat1[,-2]
summary(frm2sum <- glm(resp.frm ~ C(snconv,contr=mat1)+mprime
+mshape,data=fixw,family="quasibinomial"))
the unwanted level is still there.
But did you try:
summary(frm2sum <- glm(resp.frm ~ relevel(snconv, ref="03") + mprime +
mshape, data=fixw, family="quasibinomial"))
(The above obviously not tested on "fixw" in the absence of a
reproducible example, but was an analog modulo the minimal information
offered was tested on the quasipoisson example in help page of
"family".)
--
David.
Unbelievable.
<snarky comment deleted>
Stephen Bond
-----Original Message-----
From: David Winsemius [mailto:dwinsem...@comcast.net]
Sent: Wednesday, July 07, 2010 4:15 PM
To: Bond, Stephen
Cc: r-help@r-project.org
Subject: Re: [R] forcing a zero level in contr.sum
On Jul 7, 2010, at 4:04 PM, Bond, Stephen wrote:
Clarifying my question:
options(contrasts = c("contr.sum", "contr.poly"))
contrasts()
[,1] [,2] [,3] [,4] [,5]
01 1 0 0 0 0
03 0 1 0 0 0
05 0 0 1 0 0
06 0 0 0 1 0
07 0 0 0 0 1
09 -1 -1 -1 -1 -1
I need to force the coefficient on level 03 to be zero.
?factor
?relevel
Perhaps worth a try:
fixw$snconv <- relevel(fixw$snconv, ref="03")
(But I wonder if using contr.sum will ever generally satisfy that
goal, since contr.sum calculates the difference from a grand mean and
this will only work if a) the GM=0 and b) there is only one term on
the RHS of the model, and c) probably a bunch of other restrictions.)
--
David.
Thank you.
Stephen Bond
-----Original Message-----
From: David Winsemius [mailto:dwinsem...@comcast.net]
Sent: Wednesday, July 07, 2010 3:44 PM
To: Bond, Stephen
Cc: r-help@r-project.org
Subject: Re: [R] forcing a zero level in contr.sum
On Jul 7, 2010, at 3:13 PM, Bond, Stephen wrote:
I need to use contr.sum and observe that some levels are not
statistically different from the overall mean of zero.
What is the proper way of forcing the zero estimate? It seems the
column corresponding to that level should become a column of zeros.
Is there a way to achieve that without me constructing the design
matrix?
Thank you.
lm( formula = z ~ x + y + 0, ...) _might_ do something close to
what you want.
David Winsemius, MD
West Hartford, CT
David Winsemius, MD
West Hartford, CT
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
