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RE: st: RE: Fitting distributions to right-sensored survival data
From
"Kabaso M.E." <[email protected]>
To
"[email protected]" <[email protected]>
Subject
RE: st: RE: Fitting distributions to right-sensored survival data
Date
Fri, 24 Jan 2014 14:46:06 +0000
Dear Statalist,
As below, I can get the scale parameter p from the output. I am stuck with the scale parameter for the distribution (Weibull in this case) which I fit my data to
See the output below and kindly help
Thanks
Mushota
. streg, dist(weibull) time
failure _d: Censorship == 1
analysis time _t: (Last_StatusDate-origin)
origin: time ARV_start
id: patientIdInt
Fitting constant-only model:
Iteration 0: log likelihood = -30480.164
Iteration 1: log likelihood = -30394.76
Iteration 2: log likelihood = -30394.576
Iteration 3: log likelihood = -30394.576
Fitting full model:
Iteration 0: log likelihood = -30394.576
Weibull regression -- accelerated failure-time form
No. of subjects = 183547 Number of obs = 183547
No. of failures = 5582
Time at risk = 157273351
LR chi2(0) = 0.00
Log likelihood = -30394.576 Prob > chi2 = .
------------------------------------------------------------------------------
_t | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
_cons | 10.76499 .0470595 228.75 0.000 10.67276 10.85723
-------------+----------------------------------------------------------------
/ln_p | -.1471334 .0116291 -12.65 0.000 -.169926 -.1243409
-------------+----------------------------------------------------------------
p | .8631788 .010038 .8437273 .8830787
1/p | 1.158509 .0134724 1.132402 1.185217
------------------------------------------------------------------------------
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Kabaso M.E.
Sent: 26 November 2013 15:43
To: [email protected]
Subject: RE: st: RE: Fitting distributions to right-sensored survival data
Dear Maarten,
Thanks for your guidance.
I am able to obtain the shape parameter this way, what about the scale parameter?
Mushota
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Maarten Buis
Sent: 22 November 2013 13:08
To: [email protected]
Subject: Re: st: RE: Fitting distributions to right-sensored survival data
On Fri, Nov 22, 2013 at 1:44 PM, Kabaso M.E. wrote:
> Essentially, I can use the streg for example to fit a Weibull model to my survival data but how can I get the model's parameters for me to recreate the pdf here fitted elsewhere?
The (transformed) parameters are returned in the matrix e(b). You can also use the -[]_b[]- syntax to get at specific parameters, see: -help _variables-. Here is an example:
*------------------ begin example ------------------ sysuse cancer streg i.drug age, dist(weibull) nohr matlist e(b)
di "p = " exp([ln_p]_b[_cons])
di "1/p = " 1/exp([ln_p]_b[_cons])
*------------------- end example -------------------
* (For more on examples I sent to the Statalist see:
* http://www.maartenbuis.nl/example_faq )
Hope this helps,
Maarten
---------------------------------
Maarten L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany
http://www.maartenbuis.nl
---------------------------------
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