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Mplus Discussion > Growth Modeling of Longitudinal Data >
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 Jonathan Codell posted on Thursday, February 07, 2013 - 2:24 pm
I have 12 data points (T1-T12) and would like to model for potential cubic growth in GMM. I managed to fit a decent linear and quadratic growth models but am unclear on to determine the appropriate times in the syntax for a cubic model:

i s | T1@0 T2@1 T3@2 T4@3.........T12@11

i s q | T1@0 T2@.01 T3@.04 T4@.09......T12@1.21

What would the appropriate syntax time be for a cubic model?

i s q cub | T1@? T2@?..........T12?

Thank you for your assistance.
 Linda K. Muthen posted on Thursday, February 07, 2013 - 2:31 pm
Yes, just add a fourth growth factor.
 Jonathan Codell posted on Thursday, February 07, 2013 - 2:46 pm
Thanks for the quick response. Can you clarify exactly what you mean though. As shown in my initial post I already have four growth factors listed (i s q cub) before the "|" symbol, but I am unclear on what I should list after the "@" symbol for each of the 12 time points. Thank you for your explanation.
 Linda K. Muthen posted on Thursday, February 07, 2013 - 3:48 pm
You list the linear time scores after the | symbol. I just noticed you did this incorrectly for the quadratic model. The time scores are always the linear and Mplus computes the others. Keep the on a small scale like 0 .1 .2 etc.
 Jonathan Codell posted on Thursday, February 07, 2013 - 11:33 pm
Thank you for the clarification. It looks like I was making this more complicated than needed. I really appreciate your help.
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