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Re: st: stcrreg: graphing the interaction with time


From   Eduardo Nunez <enunezb@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: stcrreg: graphing the interaction with time
Date   Tue, 19 Oct 2010 22:54:23 -0400

Phil,

Thank you. I will follow your instructions.

Eduardo



On Tue, Oct 19, 2010 at 6:05 PM, Phil Clayton
<philclayton@internode.on.net> wrote:
>
> I would normally do the following steps:
>
> 1. Run the main model:
> stcrreg myvar ..., compete(...)
>
> 2. Add a TVC term using log(_t):
> stcrreg myvar..., compete(...) tvc(myvar) texp(log(_t))
>
> Note that myvar is in there twice, once as a constant effect and once as a TVC. If the TVC term is significant it indicates that the subhazard varies with time. If the SHR is >1 the effect increases over time; if the SHR is <1 the effect decreases with time.
>
> 3. Go back to the main model & generate Schoenfeld-like residuals:
> stcrreg myvar ..., compete(...)
> predict double res_*, schoenfeld
> twoway (scatter res_1 _t) (lowess res_1 _t, mean), title("Schoenfeld-like residuals - myvar")
>
> 4. If you need further information on the shape of the interaction, piecewise regression is probably the next step
>
> Phil
>
> On 20/10/2010, at 2:35 AM, Eduardo Nunez wrote:
>
> > Dear Statalisters:
> >
> > After running stcrreg to my data, I found that my exposure variable
> > interacted with time (using tvc) with a p-value 0.001.
> > How should I graph such interaction in order to see its direction and
> > shape? I used the default in stcrreg, meaning interacting with _t.
> > My exposure variable is continuous.
> >
> > I used Stata 11.1
> >
> > Thank you in advance,
> >
> > Eduardo
> > *
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>
>
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