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| Trouble reading longitudinal data |
 
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Hi Drs. Muthen,
For a project with longitudinal data, I've been trying to read in data from a two wave study to fit some latent growth models. However, for some reason when I run a basic analysis, all the means and covariances look nearly identical and I get a singular covariance matrix. When I run descriptives in SPSS, the means and variances look normal.
In short what I've done:
I first imputed plausible values in an R package using IRT for the variable of interest. In SPSS I have transformed the two wave data to age based variables so that I have a variable for each whole age in the dataset. The means of these age based variables look normal in SPSS. When I convert the file to csv/.dat and open te file in Mplus, the means, covariances and variances become as I described before.
Do you have any idea what might be the problem that causes the change in means and covariances/variances? |
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