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# RE: st: AW: changes in -xi: xtmixed- command from Stata 10 to 11

 From "Ploutz-Snyder, Robert (JSC-SK)[USRA]" To "statalist@hsphsun2.harvard.edu" Subject RE: st: AW: changes in -xi: xtmixed- command from Stata 10 to 11 Date Thu, 22 Apr 2010 08:42:50 -0500

```Same for me, running 10.1 on a 64bit win machine, versus 11.0 on the same machine.. both up to date with patches/upgrades.  Output:

STATA 10.1:
webuse melanoma, clear
(Skin cancer (melanoma) data)

. gen uv2 = uv^2

. xtmepoisson deaths uv uv2, exposure(expected) || nation: || region:

Refining starting values:

Iteration 0:   log likelihood = -1169.4088  (not concave)
Iteration 1:   log likelihood = -1156.8957  (not concave)
Iteration 2:   log likelihood = -1102.0609

Iteration 0:   log likelihood = -1102.0609
Iteration 1:   log likelihood = -1096.5001
Iteration 2:   log likelihood = -1089.4293
Iteration 3:   log likelihood = -1089.4112
Iteration 4:   log likelihood =  -1089.411
Iteration 5:   log likelihood =  -1089.411

Mixed-effects Poisson regression                Number of obs      =       354

--------------------------------------------------------------------------
|   No. of       Observations per Group       Integration
Group Variable |   Groups    Minimum    Average    Maximum      Points
----------------+---------------------------------------------------------
nation |        9          3       39.3         95           7
region |       78          1        4.5         13           7
--------------------------------------------------------------------------

Wald chi2(2)       =     25.69
Log likelihood =  -1089.411                     Prob > chi2        =    0.0000

------------------------------------------------------------------------------
deaths |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
uv |   .0056975   .0137931     0.41   0.680    -.0213364    .0327314
uv2 |  -.0058374    .001388    -4.21   0.000    -.0085579   -.0031169
_cons |   .1289976   .1581122     0.82   0.415    -.1808966    .4388918
expected | (exposure)
------------------------------------------------------------------------------

------------------------------------------------------------------------------
Random-effects Parameters  |   Estimate   Std. Err.     [95% Conf. Interval]
-----------------------------+------------------------------------------------
nation: Identity             |
sd(_cons) |   .4290366   .1101666      .2593735    .7096809
-----------------------------+------------------------------------------------
region: Identity             |
sd(_cons) |   .1956382   .0224569      .1562233    .2449974
------------------------------------------------------------------------------
LR test vs. Poisson regression:      chi2(2) =  1267.13   Prob > chi2 = 0.0000

Note: LR test is conservative and provided only for reference.

.

VERSUS Stata 11.0:

. gen uv2 = uv^2

. xtmepoisson deaths uv c.uv#c.uv, exposure(expected) || nation:|| region:

Refining starting values:

Iteration 0:   log likelihood = -1169.4088  (not concave)
Iteration 1:   log likelihood = -1156.8957  (not concave)
Iteration 2:   log likelihood = -1101.6231

Iteration 0:   log likelihood = -1101.6231
Iteration 1:   log likelihood = -1097.2443
Iteration 2:   log likelihood = -1089.4042
Iteration 3:   log likelihood = -1089.4016  (not concave)
Iteration 4:   log likelihood = -1089.4007
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 5:   log likelihood = -1089.4001  (backed up)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 6:   log likelihood = -1089.3999  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 7:   log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 8:   log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 9:   log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 10:  log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 11:  log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 12:  log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 13:  log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 14:  log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 15:  log likelihood = -1089.3998  (not concave)
numerical derivatives are approximate
flat or discontinuous region encountered
Iteration 16:  log likelihood = -1089.3998  (not concave)
--Break--

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Scott Merryman
Sent: Thursday, April 22, 2010 8:04 AM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: AW: changes in -xi: xtmixed- command from Stata 10 to 11.0

On Thu, Apr 22, 2010 at 7:38 AM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
> A similar thing happens when I run this example in Stata 10.1 MP:
>
>
> *************
> webuse melanoma, clear
> gen uv2 = uv^2
> xtmepoisson deaths uv uv2, exposure(expected) || nation: || region:
> *************
>
> versus this in Stata 11 MP:
>
> *************
> webuse melanoma, clear
> xtmepoisson deaths uv c.uv#c.uv, exposure(expected) || nation:|| region:
> *************
>
> The Stata 11 incarnation constantly reports "flat or discontinuous region
> encountered", while the 10.1 version converges after a couple of steps:

That's odd - I get convergence with Stata 11 MP.

. webuse melanoma, clear
(Skin cancer (melanoma) data)

. xtmepoisson deaths uv c.uv#c.uv, exposure(expected) || nation:|| region:

Refining starting values:

Iteration 0:   log likelihood = -1169.4088  (not concave)
Iteration 1:   log likelihood = -1156.8957  (not concave)
Iteration 2:   log likelihood = -1101.9749

Iteration 0:   log likelihood = -1101.9749
Iteration 1:   log likelihood = -1097.2043
Iteration 2:   log likelihood = -1089.5644
Iteration 3:   log likelihood = -1089.4115
Iteration 4:   log likelihood =  -1089.411
Iteration 5:   log likelihood =  -1089.411

Scott
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```