[R] To update() or not to update()?

[vito muggeo]

Hi Kevin,
Here there is a possible solution

Extract from the base model the response, the design matrix, (possible)
strata,....Note: fit it with argument x=T and y=T
    o<-list()
    X0<-d1.ph $x
    Y<-d1.ph $y
stra<-d1.ph $strata
....
    for(i in ....){ #what are the positions of "td" variables in the
dataframe?
            X<-cbind(X0,X[,i])
            o[[length(o)+1]]<-
agreg.fit(X,Y,strata=stra,control=coxph.control(eps =
1e-04),init=rep(0,ncol(X)), method="efron",rownames=NULL))
                   }

o is a list with all the fitted models.
agreg.fit() is faster that coxph() (that uses agreg.fit). It is something
like glm() and glm.fit().

Hope this helps you.
best,
vito


----- Original Message -----
From: "Ko-Kang Kevin Wang" <kwan022 at stat.auckland.ac.nz>
To: "R Help" <r-help at stat.math.ethz.ch>
Sent: Monday, May 19, 2003 11:31 AM
Subject: [R] To update() or not to update()?


> Hi,
>
> Suppose I have:
>   # Fit a base model
>   d1.ph <- coxph(Surv(start, stop, event)~
>                ejec + diavol + score + smoking +
>                beta + surg.done,
>                data = data.frame(foo))
>
>   summary(update(d1.ph, . ~ . + td1))
>   summary(update(d1.ph, . ~ . + td2))
>
> As I have many columns in my data frame, foo, called td's.  e.g. td1, td2,
> td3, ....  And I'd like to add one column each time.  What is the
> recommended way to do this?  Whether I should do what I did above, or
> should I do something like:
>   td1.ph <- coxph(Surv(start, stop, event)~
>                 ejec + diavol + score + smoking +
>                 beta + surg.done + td1,
>                 data = data.frame(foo))
>
>   td2.ph <- coxph(Surv(start, stop, event)~
>                 ejec + diavol + score + smoking +
>                 beta + surg.done + td2,
>                 data = data.frame(foo))
>
> I've done a system.time() on it and update() doesn't seem to be much (if
> at all) faster.  Is there an advantage of using update() then (other than
> that the codes look neater)?
>
>
> --
> Cheers,
>
> Kevin
>
> --------------------------------------------------------------------------
----
> /* Time is the greatest teacher, unfortunately it kills its students */
>
> --
> Ko-Kang Kevin Wang
> Master of Science (MSc) Student
> SLC Tutor and Lab Demonstrator
> Department of Statistics
> University of Auckland
> New Zealand
> Homepage: http://www.stat.auckland.ac.nz/~kwan022
> Ph: 373-7599
>     x88475 (City)
>     x88480 (Tamaki)
>
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