R help - May 2011 - Latent class analysis, selection of the number of classes

Hi,

I perform latent class analysis on a matrix of dichotomous variables to
create an indicator of class/category membership for each observation. I
would like to know whether there is a function that selects the best fit in
terms of number of classes/categories.

Currently, I am doing this with the lca() function of the e1071 package.
This function requires me to specify the number of classes and to compare
fit statistics for each run of lca. This becomes somewhat cumbersome the
more variables the data matrix contains and, thus, the greater the number of
possible classes is. I was wondering whether there is an alternative
implemented in a different package that does exactly that.

Thanks,
Daniel

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function ?stepFlexmix in the flexmix package may be what you're looking for
hth, Ingmar

On Mon, May 23, 2011 at 11:21 PM, Daniel Malter <daniel@umd.edu> wrote:
> Hi,
>
> I perform latent class analysis on a matrix of dichotomous variables to
> create an indicator of class/category membership for each observation. I
> would like to know whether there is a function that selects the best fit in
> terms of number of classes/categories.
>
> Currently, I am doing this with the lca() function of the e1071 package.
> This function requires me to specify the number of classes and to compare
> fit statistics for each run of lca. This becomes somewhat cumbersome the
> more variables the data matrix contains and, thus, the greater the number
> of
> possible classes is. I was wondering whether there is an alternative
> implemented in a different package that does exactly that.
>
> Thanks,
> Daniel
>
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/Latent-class-analysis-selection-of-the-number-of-classes-tp3545538p3545538.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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Dear Daniel,

the BIC can be used to estimate the number of classes. This is actually 
given out by lca, so you could run lca with several different k and pick 
the solution that gives you the best BIC.
Unfortunately I can't tell you whether "large is good" or
"small is good"
for the BIC implementation of lca, because there are both versions found 
in the literature, BIC with positive and negative sign. (I think that if 
there is any standard, then it should rather be "large is good"; you 
certainly can check it looking up the values of the loglikelihood and a 
definition of the BIC in a book. "Large is good" if the likelihood is 
used in the definition with a positive sign.)

With a bit of experimentation it should be able to find out which way 
round it is, or you may ask the e1071-maintainer.

Hope this helps (actually I may have missed if somebody responded before),
Christian

On Mon, 23 May 2011, Daniel Malter wrote:
> Hi,
>
> I perform latent class analysis on a matrix of dichotomous variables to
> create an indicator of class/category membership for each observation. I
> would like to know whether there is a function that selects the best fit in
> terms of number of classes/categories.
>
> Currently, I am doing this with the lca() function of the e1071 package.
> This function requires me to specify the number of classes and to compare
> fit statistics for each run of lca. This becomes somewhat cumbersome the
> more variables the data matrix contains and, thus, the greater the number
of
> possible classes is. I was wondering whether there is an alternative
> implemented in a different package that does exactly that.
>
> Thanks,
> Daniel
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Latent-class-analysis-selection-of-the-number-of-classes-tp3545538p3545538.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
*** --- ***
Christian Hennig
University College London, Department of Statistical Science
Gower St., London WC1E 6BT, phone +44 207 679 1698
chrish at stats.ucl.ac.uk, www.homepages.ucl.ac.uk/~ucakche