[R] AFTREG with ID argument

[Göran Broström]

On Fri, Feb 5, 2010 at 11:30 AM, Philipp Rappold
<philipp.rappold at gmail.com> wrote:
> Dear all,
>
> I have some trouble using the "id"-argument with aftreg (accelerated failure
> time regression analysis from the eha library).
>
> As far as I understand it, the id argument is used to group individuals
> together if there are time-varying covariates and the data is arranged in
> counting process style.
>
> Unfortunately, i cannot figure out how to use the "id"-argument. The most
> straight-forward way would be to simply state the grouping variable, but it
> throws an error. I've included an example below: the dataframe for
> regression is called "test", with the grouping variable "person".
>
>> test
>  start end censor person var1
> 1     0   1      0      1  0.5
> 2     1   2      0      1  0.4
> 3     2   3      0      1  0.6
> 4     3   4      1      1 -0.3
> 5     0   1      0      2  0.6
> 6     1   2      0      2  0.7
> 7     2   3      0      2  0.6
>
>> fit <- aftreg(Surv(start, end, censor)~var1, data=test, id=person)
> Error in order(id, Y[, 1]) : argument 1 is not a vector

You have caught the _function_ 'person' (package: utils) instead of
the variable 'person' in the data frame. That explains the odd error
message. If you change the variable name to, e.g., "ID", you'll get
the error message

Error in order(id, Y[, 1]) : object 'id' not found

which would hint you in the right direction. You need to specify  'id'
by a full name, in your case 'test$person'. This is of course a
deficiency in the interface of aftreg. I will fix it asap.

So the temporary fix is 'id = test$person'.

Thanks for the report,

Göran

>> fit <- aftreg(Surv(start, end, censor)~var1, data=test, id=test["person"])
> Error in `[.data.frame`(id, ord) : undefined columns selected
>
>
>
> What would be the correct way to fit this example model?
>
> Thanks + all the best
> Philipp
>
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-- 
Göran Broström