.-
help for ^lrchg^
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Calculates change in coefficients between logistic models
----------------------------
^lrchg^ , store(n)
or
^lrchg^ , contr(n m)
Description
-----------
^lrchg^ displays the coefficients in two logistic models, and
calculates the proportion of change in coefficients between two
models.
This is useful in logistic regression modelling in epidemiology.
Use
^lrchg^ , store(1)
^lrchg^ , store(2)
^lrchg^ , contr(1 2)
to store two models, then contrast them.
Options
-------
store(n)
Stores logistic regression results in a variable coeffn
Use before contrasting two models.
contr(n m)
Contrasts two models previously stored.
nocoeff
Drop the calculations of changes in coefficients.
Examples
--------
. xi: logistic response i.agek6 i.gend i.agek6*i.gend i.regio
. lrchg, store(0)
. xi: logistic response i.agek6 i.gend i.agek6*i.gend
. lrchg, store(1)
. lrchg, contr(0 1)
Likelihood ratio tests and change in coefficients
between logistic regression models
--------------------------------------------------
Diff. in LL = 99.855
Diff. in df = 1
P-value = 0.0000
Change in common coefficients
between models 0 and 1:
Coefficient Model 0 Model 1 %change
--------------------------------------------------
Iage_1 0.9293 0.8923 4.0
Iage_2 1.2648 1.2064 4.6
Igend_2 1.6332 1.6133 1.2
IaXg_1_2 0.9801 0.9834 -0.3
IaXg_2_2 0.9768 0.9848 -0.8
--------------------------------------------------
Iregio_2 0.9293 0.0000 uniq
Remarks
-------
Presently the coefficients are stored in matrices named
coeff`n'. This shouldn't cause any problems, but it is
not elegant.
It might be better to use -estimates hold- but will
have to get back to this.
The author wonders what to do if there are zero degrees
of freedom ?
Inspired by the program lrdrop1 by Zhiqiang Wang.
Author
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Jan Brogger, University of Bergen, Norway
jan.brogger@@med.uib.no (21 May 2000)
Shameless plug :)
--------------
I am looking for internship & residency in internal
medicine/pulmonary medicine US/EU. Am doing PhD in respiratory
epidemiology now.