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st: RE: question


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: question
Date   Thu, 3 Nov 2005 11:38:42 -0000

First, note that the title "question" is not informative. 

You have two questions. On the second, there is an FAQ 

FAQ     . . . . . . . . . . . . . . . . . . . . . . . Replacing missing values
        2/03    How can I replace missing values with previous or
                following nonmissing values?
                http://www.stata.com/support/faqs/data/missing.html

. search missing 

points to this. 

On the first, I am no survival expert, 
but absent a view of all your data your question looks very 
difficult to answer. But you can at a minimum compare the results on 
non-missing data and on data including imputations to see 
what difference it makes. 

Nick 
n.j.cox@durham.ac.uk 

Scott Cunningham
 
> I am estimating a hazard, but I am missing data for certain time- 
> variant covariates when t is very small.  Seeing data will help me  
> explain this.
> 
> +--------------------------------+
>       |       sr   _st   _d   _t   _t0 |
>       |--------------------------------|
>    1. |        .     1    0    1     0 |
>    2. |        .     1    0    2     1 |
>    3. |        .     1    0    3     2 |
>    4. |        .     1    0    4     3 |
>    5. |        .     1    0    5     4 |
>       |--------------------------------|
>    6. |        .     1    0    6     5 |
>    7. |        .     1    0    7     6 |
>    8. |        .     1    0    8     7 |
>    9. |        .     1    0    9     8 |
> 10. | .9738716     1    0   10     9 |
>       |--------------------------------|
> 11. | 1.081043     1    0   11    10 |
> 12. |  1.21261     1    0   12    11 |
> 13. | 1.125889     1    1   13    12 |
> 14. |        .     1    0    1     0 |
> 15. |        .     1    0    2     1 |
>       |--------------------------------|
> 16. |        .     1    0    3     2 |
> 17. |        .     1    0    4     3 |
> 18. |        .     1    0    5     4 |
> 19. |        .     1    0    6     5 |
> 20. |        .     1    0    7     6 |
>       |--------------------------------|
> 21. |        .     1    0    8     7 |
> 22. |        .     1    0    9     8 |
> 23. | .9738716     1    0   10     9 |
> 24. | 1.081043     1    0   11    10 |
> 25. |  1.21261     1    0   12    11 |
>       |--------------------------------|
> 26. | 1.125889     1    0   13    12 |
> 27. | 1.080463     1    0   14    13 |
> 28. | .9527455     1    1   15    14 |
> 
> 
> Notice that for all values of t=0 to t=9, I am missing data for sr.   
> My first question is when I -streg-, what effect does this 
> have on my  
> estimation?  None of my respondents complete their respective spells  
> prior to t=10.  Secondly, assume I wanted to fill in those missing  
> values with the same value as t=10.  How would I do this?

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