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Mplus Discussion > Growth Modeling of Longitudinal Data >
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 Joo-Young Lee posted on Monday, April 14, 2008 - 6:42 pm
Hi.

I am planning to do some growth mixture modeling with adolescent longitudinal data in Korea.

Is there any way to identify a certain subgroup which considers growth in two parallel dependent variables such as depression and delinquency?

I am hoping to find a subgroup of adolescents who are both high in depression and deliquency over 2 years of assessment with 4 timepoints.

Since I am just beginning to study mplus software, would you provide any tips to write an appropriate syntax for this kind of modeling?

Thank you.
 Linda K. Muthen posted on Tuesday, April 15, 2008 - 9:01 am
You would need to start with a parallel process growth model like the one shown in Example 6.13 and add TYPE=MIXTURE; and one latent class variable using the CLASSES option of the VARIABLE command. For that see Example 8.1.
 Joo-Young Lee posted on Wednesday, April 16, 2008 - 1:00 am
Thank you very much for your kind help.

I have one more question about my study.

My study follows a cohort-sequential design.
I have transformed my data set and it looks like the one shown in page 405 of User's guide. For this data set, I would like to apply FIML for missing data. In order to do this, is it correct to simply write "TYPE=MIXTURE missing;"?

Following your guidance, is it right to include below commands for my study?

==========

VARIABLE : CLASSES = c (1) ;

ANALYSIS : TYPE = MIXTURE missing ;

MODEL :

%OVERALL%
i1 s1 | y11@0 y12@1 y13@2 y14@3 ;
i2 s2 | y21@0 y22@1 y23@2 y24@3 ;
s1 ON i2 ;
s2 ON i1 ;
i1 s1 ON X ;
i2 s2 ON X ;
c ON X ;

==========

I really appreciate your guidance and help for this matter.
 Linda K. Muthen posted on Wednesday, April 16, 2008 - 6:11 am
This looks correct. I would however start with a model without covariates.
 Joo-Young Lee posted on Wednesday, April 16, 2008 - 6:14 pm
Again, thank you for your tips!
 Joo-Young Lee posted on Friday, April 18, 2008 - 4:27 am
Dear Linda,

I actually tried to run a growth mixture model with above syntax. And I started with a model without covariates.

However, it seems like that I have a problem with convergence.

I keep getting the same warning message as following:

THE ESTIMATED COVARIANCE MATRIX FOR THE Y VARIABLES IN CLASS 1 COULD NOT
BE INVERTED. PROBLEM INVOLVING VARIABLE B7. COMPUTATION COULD
NOT BE COMPLETED IN ITERATION 2. CHANGE YOUR MODEL AND/OR STARTING
VALUES.

THE MODEL ESTIMATION DID NOT TERMINATE NORMALLY DUE TO AN ERROR IN THE
COMPUTATION. CHANGE YOUR MODEL AND/OR STARTING VALUES.


Could you please provide any tips to solve this kind of problem?

I am VERY VERY new to Mplus, and I am having a tough time studying this on my own.

If I want to specify starting values, what kind of procedure is needed?

Thank you very much.
 Linda K. Muthen posted on Friday, April 18, 2008 - 6:30 am
You can read about assigning starting values in the user's guide. I suggest you send your input, data, output, and license number to support@statmodel.com.
 Joo-Young Lee posted on Friday, October 17, 2008 - 12:28 am
Dear Linda,

Is there any way to exclude the default setting of correlation between slope growth factors in Example 6.13 of parallel processes?

And can I see the correlation between intercept and slope in each process?
(What is the correct syntax for this?)

In a longitudinal data, one can usually assume that residuals of indicators are high correlated.

In Example 6.13, how can I specify that residuals from y11 to y14 are correlated or same?


Thank you very much for your help.
 Linda K. Muthen posted on Friday, October 17, 2008 - 6:00 am
You can fixed the covariance between the slope growth factors at zero as follows:

s1 WITH s2@0;

You can specify the covariance between the intercept and slope growth factors as follows:

i1 WITH s1;

Residual covariances are specified using the WITH option, for example,

y11 WITH y12;

Equalities of the residual covariances are specified as follows:

y11 WITH y12-y14 (1);
y12 WITH y13-y14 (1);
y13-y14 (1);

Please see Chapter 16 of the user's guide for more information.
 Joo-Young Lee posted on Friday, October 17, 2008 - 7:20 am
Thank you very much for your prompt reply!
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