R help - Jul 2001 - using identity link for binomial familly with glm

-- Error in binomial(link = "identity") : identity link not available
for binomial family, available links are "logit", 
"probbit", "cloglog" and "log"

Hi, I have a question, dealing with this error response. I'm trying to 
make anova on percentages. The variablethat has a biological 
significance is actually the percentage itself. Is it really not 
possible, to test a simple linear probability model with glm, using 
binomial model and identity link function ? I know it's hard to deal 
with probability responses out of [0,1] but well... help me !
There is an example of such a linear probability model in Agresti (1997) 
some software aparently do it
Thanks,
St?phane



--


St?phane DUPAS

IRD c/o CNRS
Lab P.G.E., Bat 13,
1 av terrasse
91198 Gif sur Yvette
tel 33 1 69 82 37 04


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

On Tue, 31 Jul 2001, Stephane Dupas wrote:
> -- Error in binomial(link = "identity") : identity link not
available for binomial family, available links are "logit", 
"probbbit", "cloglog" and "log"
>
> Hi, I have a question, dealing with this error response. I'm trying to
> make anova on percentages. The variablethat has a biological
> significance is actually the percentage itself. Is it really not
> possible, to test a simple linear probability model with glm, using
> binomial model and identity link function ? I know it's hard to deal
> with probability responses out of [0,1] but well... help me !
> There is an example of such a linear probability model in Agresti (1997)
> some software aparently do it
You can do it easily: use a quasi model.

quasi(link = "identity", variance = "mu(1-mu)")

I believe.  You will probably need to specify a good starting value.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._