On Mon, May 2, 2011 at 5:38 PM, Mike Harwood <harwood...@gmail.com> wrote:
> Hello,
>
> I am apparently confused about the use of an id parameter for an event
> history/survival model, and why the EHA documentation for aftreg does
> not specify one. All assistance and insights are appreciated.
Which version of eha are you using? The latest version documents the
use of 'id'.
> Attempting to specifiy an id variable with the documentation example
> generates an "overlapping intervals" error,
Thanks for pointing this out. It is an error (actually three) in the
data frame.
The reason is that it is "real" data; and not sufficiently checked by me.
I'll fix this in an update soon.
Thanks again,
Göran
so I sorted the original
> mort dataframe and set subsequent entry times an id to the previous
> exit time + 0.0001. This allowed me to see the affect of the id
> parameter on the coefficients and significance tests, and prompted my
> question. The code I used is shown below, with the results at the
> bottom. Thanks in advance!
>
> Mike
>
> head(mort) ## data clearly contains multiple entries for some of the
> dataframe ids
>
> no.id.aft <- aftreg(Surv(enter, exit, event) ~ ses, data = mort) ##
> Inital model
> id.aft <- aftreg(Surv(enter, exit, event) ~ ses, data = mort, id=id)
> ## overlapping intervals error
>
> mort.sort <- ## ensure records ordered
> mort[
> order(mort$id, mort$enter),]
>
> ## remove overlap
> for (i in 2:nrow(mort.sort)){
> if (mort.sort[i,'id'] == mort.sort[i-1,'id'])
> mort.sort[i,'enter'] <- mort.sort[i-1, 'exit'] + 0.0001
> }
>
> no.id.aft.sort <- aftreg(Surv(enter, exit, event) ~ ses, data =
> mort.sort) ## initial model on modified df
> id.aft.sort <- aftreg(Surv(enter, exit, event) ~ ses, id=id, data =
> mort.sort) ## with id parameter
>
>
> #=== output ===========#
>> no.id.aft.sort
> Call:
> aftreg(formula = Surv(enter, exit, event) ~ ses, data = mort.sort)
>
> Covariate W.mean Coef Exp(Coef) se(Coef) Wald p
> ses
> lower 0.416 0 1 (reference)
> upper 0.584 -0.347 0.707 0.089 0.000
>
> log(scale) 3.603 36.704 0.065 0.000
> log(shape) 0.331 1.393 0.058 0.000
>
> Events 276
> Total time at risk 17045
> Max. log. likelihood -1391.4
> LR test statistic 16.1
> Degrees of freedom 1
> Overall p-value 6.04394e-05
>> id.aft.sort
> Call:
> aftreg(formula = Surv(enter, exit, event) ~ ses, data = mort.sort,
> id = id)
>
> Covariate W.mean Coef Exp(Coef) se(Coef) Wald p
> ses
> lower 0.416 0 1 (reference)
> upper 0.584 -0.364 0.695 0.090 0.000
>
> log(scale) 3.588 36.171 0.065 0.000
> log(shape) 0.338 1.402 0.058 0.000
>
> Events 276
> Total time at risk 17045
> Max. log. likelihood -1390.8
> LR test statistic 17.2
> Degrees of freedom 1
> Overall p-value 3.3091e-05
>>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Göran Broström
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
