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RE: st: ice and random-number seed

From   "Medina, Tait Runnfeldt" <>
To   "Rodrigo Alfaro A." <>, ""<>
Subject   RE: st: ice and random-number seed
Date   Fri, 22 Aug 2008 15:35:22 -0400

Thank you. Your point about "order matters" made me remember the -orderasis- option. The fix I suggested earlier (setting the seed manually prior to both -ice- and -mim-) doesn't seem to work if you are using weights...but using both the -orderasis- and the -seed- options of -ice- seems to fix the problem.

-----Original Message-----
From: Rodrigo Alfaro A. []
Sent: Friday, August 22, 2008 10:16 AM
Cc: Medina, Tait Runnfeldt
Subject: RE: st: ice and random-number seed



I think that your case is more complicated than Maarten's example.

(1) You are using weights. If I recall correctly ICE produces results
using iterations => order matters. My suggestion is to try your problem
without weights.

(2) Sorting could make some differences here. You could try imputing
one dataset each time using a specific seed. It is expected the
correlations between imputed variables (original y replication) should
be one.

Under (1) you have no solution. Under (2) you could control the problem
imputing 1 dataset at the time with specific seeds. We had problem (2)
with user-written routine hotdeck.


-----Mensaje original-----
[] En nombre de Medina, Tait
Enviado el: Viernes, 22 de Agosto de 2008 08:15 a.m.
Asunto: RE: st: ice and random-number seed

Dear Richard:

Thank you for your reply.

I tried using -mim- and version 1.4.6 PR 25apr2008 of -ice-, but I am
still unable to reproduce results.

On a side note, I was under the impression that the command -adoupdate-
would update user-written packages, but the command failed to update my
installed -ice- package. Am I mistaken in my understanding of this


-----Original Message-----
[] On Behalf Of Richard
Sent: Friday, August 22, 2008 12:36 AM
Subject: Re: st: ice and random-number seed

At 09:43 PM 8/21/2008, Medina, Tait Runnfeldt wrote:
>I am unable to reproduce regression results using imputed data
>generated via Royston's -ice- command, although I am using the
>-seed- option. A comparison of a mock original and an attempted
>replication, illustrating this problem, can be found in step #4 below.
>I am using Stata version 10.1. The version of -ice- and -micombine-
>being used can be found in step #5 below.

You might also try -mim- instead of -micombine-.  I'm not sure why both
exist since Royston is an author of both, but my impression is that
-mim- is better.  You may need to rename some of the vars created by
-ice-. -mim- is available on SSC.

Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu

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