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Re: st: Ask for help regarding colelms


From   Paul Seed <paul.seed@kcl.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Ask for help regarding colelms
Date   Wed, 15 Nov 2006 14:20:03 +0000

Hao Thi Duong asked about the command -colelms-,
which calculates Cole's LMS values for growth data.

The help file is very brief, and does not properly explain what
the program does.  The program is described as version 0.2;
implying it is really pre-first release.   It has the very odd
undocumented property of dropping all variables & records
not needed in the calculations;  so it is advisable to save
your data set before using.

The missing values are apparently in sparse areas of
the data where there is only a single value &
the SD cannot be calculated.

To understand how to set the df term, Hao would need to read
Tim Cole's articles on the method.
 To understand the program, he might contact the authors
 Author:  Zhiqiang Wang, Menzies School of Health Research
Support: email  wang@menzies.edu.au

Author:  Mark S Pearce, University of Newcastle upon Tyne
Support: email  m.s.pearce@newcastle.ac.uk

However, I would recommend he use
the -xrigls- and -xriml- commands, which do essentially
the same job, and are much better documented & explained.
There are many methods for fitting reference lines.

Paul Seed

Date: Mon, 13 Nov 2006 22:35:38 -0600
From: "Duong, Hao Thi" <Hao.T.Duong@uth.tmc.edu>
Subject: st: Ask for help regarding colelms

Dear
I would like to ask for your help about the command colelms.
The command runs funny to me:
. colelms BMI_b, agegroup(cdcage_b) sex(gender) nosmooth
(10 missing values generated)
(10 missing values generated)
(10 missing values generated)
(10 missing values generated)
(10 missing values generated)
First, it gives missing values. Second, it calculates once for observations have the same agegroup. Although age is same, sex and BMI are diffirent so i expect to see different L, M, and S values.
Also, I do not know how to set the value of df and its function in this command in the syntax below given by "help"
colelms yvar, agegroup(var) [sex(var) centile(# # #) df(#) nosmooth]
If anyone knows, please help.
Thank you


Hao Duong, M.D., M.P.H.
Dr.P.H. Candiate in Health Promotion & Health Education
University of Texas Health Science Center Houston,
School of Public Health
Email: hao.t.duong@uth.tmc.edu

=========================
Paul T Seed, MSc CStat
Lecturer in Medical Statistics
King's College London,
Division of Reproduction and Endocrinology



St Thomas' Hospital,
Lambeth Palace Road,
London SE1 7EH

Funded by the Wellcome Trust & Tommy's the Baby Charity
http://www.mfru.info/lecturenotes.html


(Paul.Seed@kcl.ac.uk)
tel   (+44) (0) 20 7188 3642
fax (+44) (0) 20 7620 1227



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