R help - Feb 2010 - SEM error

I'm trying to do some confirmatory factor analysis on some data. My SEM
model solves in 22 iterations, but when I try to look at the modification
indices, using mod.indices, I get the following error message:

Error in solve.default(hessian) :
  system is computationally singular: reciprocal condition number 4.40283e-18

What does this mean?

Many thanks,

Dan

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On 20.02.2010 08:51, Dan Edgcumbe wrote:
> I'm trying to do some confirmatory factor analysis on some data. My SEM
> model solves in 22 iterations, but when I try to look at the modification
> indices, using mod.indices, I get the following error message:
>
> Error in solve.default(hessian) :
>    system is computationally singular: reciprocal condition number >
4.40283e-18
>
> What does this mean?
That the method you apply tries to invert some object called "hessian"
(maybe a hessian? ;-)) but fails since a singular matrix cannot be 
inverted. Perhaps (as I often found for people doing sem analyses) you 
have less observations than parameters to estimate or only certain 
combinations for some factors?

Uwe Ligges




>
> Many thanks,
>
> Dan
>
> 	[[alternative HTML version deleted]]
>
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