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Re: st: "not concave"

From   Wahideh Achbari <>
Subject   Re: st: "not concave"
Date   Fri, 1 Mar 2013 14:24:38 +0100

Thanks for this Nick. Here is the syntax:

sem (Poleff -> opinion_not_vote) (Poleff -> say_pol) (Poleff ->
care_pol) (Poleff -> pol_not_complex), method(mlmv) standardized
latent(Poleff ) nocapslatent
(47 all-missing observations excluded)

There was no fit at all as the iterations kept running with "not
concave" in brackets.

If you need the data I can also send that.

Thanks again,

On 1 March 2013 14:18, Nick Cox <> wrote:
> It's not the model; it's your log-likelihood function that is awkward
> over part of the parameter space.
> It's important to realise also that maximum likelihood is emphatically
> not an algorithm. It is an estimation method.
> This isn't necessarily a big problem. Nor is the absence of warning
> messages from other software necessarily diagnostic. Perhaps Stata is
> just more explicit, or they used different algorithms to implement
> their fits. It's difficult to say.
> However, it is not clear from your post whether the command you used
> -- not even spelled out here -- converged to give a fit.
> To say more experts in this technique (not me) would need to see your
> command syntax and results from Stata.
> Your post is strong on "I think I have a problem" but much more
> context is needed for a fuller answer. See the FAQ on advice on this.
> Nick
> On Fri, Mar 1, 2013 at 12:55 PM, Wahideh Achbari
> <> wrote:
>> Here's a query about a very simple confirmatory factor analysis with 4
>> factors. I have been trying to estimate this model, but unfortunately
>> the model is "not concave" running a Maximum Liklihood algorithm. What
>> surprises me most is that I have been running the same model in AMOS
>> and MPLUS without any difficulties. I would like to know what can be
>> done to remedy this. Your help is greatly appreciated.
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