[R] How to get the variables used in stepwise logistic regression?

[Soyeon Kim]

Thank you. This is what I want.
I need to study about attr :).

Soyeon

On Fri, Feb 4, 2011 at 11:07 AM, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Feb 4, 2011, at 11:56 AM, Soyeon Kim wrote:
>
>> Dear All,
>>
>> I used glm and then used step function for stepwise regression.
>> Now, I want to store the variables used in the stepwise regression.
>
> I am not sure that what you ask here is actually what you eventually ask and
> will limit my answer to only what you ask below.
>
>>
>> The code is the following.
>>
>> m_logistic <- glm(y ~ . + M1:T + M2:T + M3:T+ M4:T +M5:T,
>> family=binomial("logit"), data = data)
>>  step_glm <- step(m_logistic)
>>
>>> step_glm$terms
>>
>> y ~ M1 + T + M1:T
>> attr(,"variables")
>> list(y, M1, T)
>> attr(,"factors")
>>  M1 T M1:T
>> y   0 0    0
>> M1  1 0    1
>> T   0 1    1
>> attr(,"term.labels")
>> [1] "M1"   "T"    "M1:T"
>> attr(,"order")
>> [1] 1 1 2
>> attr(,"intercept")
>> [1] 1
>> attr(,"response")
>> [1] 1
>> attr(,".Environment")
>> <environment: R_GlobalEnv>
>> attr(,"predvars")
>> list(y, M1, T)
>> attr(,"dataClasses")
>>       y        M1         T
>> "numeric" "numeric" "numeric"
>>
>> How can I extract only "term.labels" ?
>>
>
> Have you tried what would seem to be the obvious answer (assuming that is a
> faithful console output):
>
> attr(step_glm$terms,  "term.labels")
>
> ?attr
> ?attributes
>
> (And the usual caveats: stepwise methods are often invalid.)
>
> --
> David Winsemius, MD
> West Hartford, CT
>
>