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Re: st: Cox model with a segmented time-dependent covariate
From
William Buchanan <[email protected]>
To
[email protected]
Subject
Re: st: Cox model with a segmented time-dependent covariate
Date
Wed, 15 Jan 2014 12:50:37 -0600
Again, it would be very helpful if you provided the syntax (in _Stata_) that you've already used with limited success if you'd like people to provide you with meaningful/useful answers to your query. Although showing the SPSS equivalent may be helpful for some Stata users, it's unlikely to mean much to the majority of Stata users who may be able to better explain where things went wrong for you if you provide the syntax that you've been trying.
HTH,
Billy
On Jan 15, 2014, at 12:47 PM, Marta Garcia-Granero <[email protected]> wrote:
> El 15/01/2014 19:42, William Buchanan escribió:
>> Please provide the exact syntax you entered into Stata in addition to the output.
>
> The output is SPSS' not Stata's. I have not been able to replicate the results in Stata, that's why I'm asking for help.
>
> Regards,
> Marta
>>
>> Thank you,
>> Billy
>>
>> On Jan 15, 2014, at 12:27 PM, Marta Garcia-Granero <[email protected]> wrote:
>>
>>> I am trying to replicate some SPSS commands in Stata. This data were modified from David Collett (2003) Modelling Survival Data in Medical Research (Chapman & Hall/CRC Texts in Statistical Science), and show a hypothetical clinical trial on 12 patients. I want to test if treatment is significant, adjusted for age and ln(bilirrubin). Ln(bilirrubin) were measured 3 times: at baseline (lbr0); approximately at 3 months -with the exact day recorded in t1 (lbr1); and approximately at 6 months - with exact day recorded in t2 (lbr2).
>>>
>>> +----------------------------------------------------------------------------+
>>> | patient time status treatment age lbr0 t1 lbr1 t2 lbr2 |
>>> |----------------------------------------------------------------------------|
>>> 1. | 1 281 Died Placebo 46 3.2 47 3.8 184 4.9 |
>>> 2. | 2 604 Alive Placebo 57 3.1 94 2.9 187 3.1 |
>>> 3. | 3 457 Died Placebo 56 2.2 61 2.8 97 2.9 |
>>> 4. | 4 384 Died Placebo 65 3.9 92 4.7 194 4.9 |
>>> 5. | 5 341 Alive Placebo 73 2.8 87 2.6 192 2.9 |
>>> |----------------------------------------------------------------------------|
>>> 6. | 6 842 Died Placebo 64 2.4 94 2.3 197 2.8 |
>>> 7. | 7 1514 Died Treatment 69 2.4 74 2.9 202 3 |
>>> 8. | 8 182 Alive Treatment 62 2.4 90 2.5 182 2.9 |
>>> 9. | 9 1121 Died Treatment 71 2.5 101 2.5 410 2.7 |
>>> 10. | 10 1411 Alive Treatment 69 2.3 182 2.2 847 2.8 |
>>> |----------------------------------------------------------------------------|
>>> 11. | 11 814 Died Treatment 77 3.8 167 3.9 498 4.3 |
>>> 12. | 12 1071 Died Treatment 58 3.1 108 2.8 187 3.4 |
>>> +----------------------------------------------------------------------------+
>>>
>>> With SPSS, I had to define a time varying covariate (T_COV_) and add it to the model:
>>>
>>> TIME PROGRAM.
>>> COMPUTE T_COV_ = (T_<t1)*lbr0 + (T_>=t1&T_<t2)*lbr1 + (T_>=t2)*lbr2.
>>> COXREG time
>>> /STATUS=status(1)
>>> /CONTRAST (treatment)=Indicator
>>> /METHOD=ENTER T_COV_ treatment age.
>>>
>>> In SPSS, T_ is the same as Stata's _t.
>>>
>>> This is the output:
>>> coef se HR ----95%CI------ LR de sig
>>> T_COV_ 4.533 2.488 93.05 0.71 12192.54 10.865 1 0.001
>>> Treatment 4.749 2.860 115.50 0.42 31421.66 5.814 1 0.016
>>> Age -0.078 0.094 0.93 0.77 1.11 0.808 1 0.369
>>>
>>> With Stata, I suspect I have to use, somehow, -stsplit- and -stjoin- , but I can't figure how (even though I have used help stsplit, and read the whole PDF on stcox).
>>>
>>> Any hints?
>>>
>>> Thanks,
>>> Marta Garcia-Granero
>>>
>>> *
>>> * For searches and help try:
>>> * http://www.stata.com/help.cgi?search
>>> * http://www.stata.com/support/faqs/resources/statalist-faq/
>>> * http://www.ats.ucla.edu/stat/stata/
>>
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/faqs/resources/statalist-faq/
>> * http://www.ats.ucla.edu/stat/stata/
>>
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/faqs/resources/statalist-faq/
> * http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/faqs/resources/statalist-faq/
* http://www.ats.ucla.edu/stat/stata/