R help - Aug 2003 - logistic regression without intercept

I want to do a logistic regression without an intercept term.  This
option is absent from glm, though present in some of the inner functions
glm uses.  I gather glm is the standard way to do logistic regression in
R.

Hoping it would be passed in, I said
> r <- glm(brain.cancer~epilepsy+other.cancer, c3, 
>        family=binomial(link="logit"), intercept=FALSE)
which produced
Error in glm.control(...) : unused argument(s) (intercept ...)

Is there an easy way to do this?  I suppose I could start hacking away
at glm so it would take the argument and pass it on, but is it absent
for a reason?

Also, I noticed that S-Plus but not R has a glim routine that uses
maximum likelihood.  What would be the equivalent?

Thanks.

On Tue, 19 Aug 2003, Ross Boylan wrote:
> I want to do a logistic regression without an intercept term.  This
> option is absent from glm, though present in some of the inner functions
> glm uses.  I gather glm is the standard way to do logistic regression in
> R.
>
> Hoping it would be passed in, I said
> > r <- glm(brain.cancer~epilepsy+other.cancer, c3,
> >        family=binomial(link="logit"), intercept=FALSE)
> which produced
> Error in glm.control(...) : unused argument(s) (intercept ...)
>
> Is there an easy way to do this?  I suppose I could start hacking away
> at glm so it would take the argument and pass it on, but is it absent
> for a reason?
Yes. You specify no intercept  with the formula:
r <- glm(brain.cancer~epilepsy+other.cancer+0, c3,
        family=binomial(link="logit"), intercept=FALSE)
or
r <- glm(brain.cancer~epilepsy+other.cancer-1, c3,
        family=binomial(link="logit"), intercept=FALSE)

The latter is S-PLUS compatible
> Also, I noticed that S-Plus but not R has a glim routine that uses
> maximum likelihood.  What would be the equivalent?
glm.

	-thomas

Did you try the following:

 >>r <- glm(brain.cancer~epilepsy+other.cancer-1, c3,
 >>       family=binomial(link="logit") )

The construct "-1" on the right hand side of a formula means to
exclude
the intercept.  See, e.g., "model formulae" in the index to Modern 
Applied Statistics with S by Venables & Ripley.  I don't remember doing 
this with glm, but I've done it with lm.

hope this helps.  spencer graves

Ross Boylan wrote:
> I want to do a logistic regression without an intercept term.  This
> option is absent from glm, though present in some of the inner functions
> glm uses.  I gather glm is the standard way to do logistic regression in
> R.
> 
> Hoping it would be passed in, I said
> 
>>r <- glm(brain.cancer~epilepsy+other.cancer, c3, 
>>       family=binomial(link="logit"), intercept=FALSE)
> 
> which produced
> Error in glm.control(...) : unused argument(s) (intercept ...)
> 
> Is there an easy way to do this?  I suppose I could start hacking away
> at glm so it would take the argument and pass it on, but is it absent
> for a reason?
> 
> Also, I noticed that S-Plus but not R has a glim routine that uses
> maximum likelihood.  What would be the equivalent?
> 
> Thanks.
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

Thanks to Thomas Lumley, Spencer Graves, and Steve Sullivan for their
advice on and off list to modify the formula with +0 (which I did; it
worked) or -1 at the end.

A couple of items of clarification:

, On Tue, 2003-08-19 at 15:32, Thomas Lumley wrote:
> On Tue, 19 Aug 2003, Ross Boylan wrote:
> 
> > I want to do a logistic regression without an intercept term.  This
> > option is absent from glm, though present in some of the inner
functions
> > glm uses.  I gather glm is the standard way to do logistic regression
in
> > R.
> >
> > Hoping it would be passed in, I said
> > > r <- glm(brain.cancer~epilepsy+other.cancer, c3,
> > >        family=binomial(link="logit"), intercept=FALSE)
> > which produced
> > Error in glm.control(...) : unused argument(s) (intercept ...)
> >
> > Is there an easy way to do this?  I suppose I could start hacking away
> > at glm so it would take the argument and pass it on, but is it absent
> > for a reason?
> 
> Yes. You specify no intercept  with the formula:
> r <- glm(brain.cancer~epilepsy+other.cancer+0, c3,
>         family=binomial(link="logit"), intercept=FALSE)
> or
> r <- glm(brain.cancer~epilepsy+other.cancer-1, c3,
>         family=binomial(link="logit"), intercept=FALSE)
> 
> The latter is S-PLUS compatible
Omit the intercept=FALSE in the above lines; it causes an error even
with the augmented model spec.
> 
> > Also, I noticed that S-Plus but not R has a glim routine that uses
> > maximum likelihood.  What would be the equivalent?
> 
> glm.
> 
I thought glm was a minimize the deviations approach, which is different
from maximize likelihood.
> 	-thomas
> 
> 
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