help: error in fn(x, ...): Downdated VtV is not positive definite
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On Thu, Jul 19, 2018 at 4:49 PM Ahreum Maeng <amaengwork at gmail.com> wrote:
1) Okay, I centered all the numeric variables and ran the model again. I did not get the error message and the model ran and I was able to get the summary results. However, I got the following warning message. Would this warning be a problem? med.fit <- lmer(situ.cent ~ cult.cont*change.cent + (change.cent || id), data = tidy.total, REML=FALSE) Warning messages: 1: In optwrap(optimizer, devfun, getStart(start, rho$lower, rho$pp), : convergence code 3 from bobyqa: bobyqa -- a trust region step failed to reduce q 2: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, : unable to evaluate scaled gradient 3: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, : Model failed to converge: degenerate Hessian with 2 negative eigenvalues
The bobyqa error means the model got stuck somewhere, this may or may not be important (see https://stats.stackexchange.com/questions/89945/meaning-of-a-convergence-warning-in-glmer for more discussion). The standard suggestion is to try with another optimizer and compare results (see `?troubleshooting` and `?convergence`). The fact that the Hessian has negative eigenvalues probably means the model is singular. Are some of your estimated random-effects standard deviations zero or very close to zero? That may be ignorable (see the GLMM FAQ), but in general means your model is more complex than your data can support.
2) I ran another related model with the same data set using the following model. But I get the error message saying that the grouping factor specification is invalid. How could I fix this issue? out.fit <- lmer(rating.cent ~ situ.cent*cult.cont*change.cent + (change.cent || id), data = tidy.total, REML=FALSE) Error: Invalid grouping factor specification, id
Pretty much impossible to say without a reproducible example. Is 'id' definitely a factor within tidy.total? (It should work anyway if it's (1) not a factor [it will be converted] and (2) not in tidy.total [it will be taken from the environment], but both of these cases will improve the chances of everything working OK.)
Many thanks, Ahreum On Thu, Jul 19, 2018 at 2:37 PM, Ahreum Maeng <amaengwork at gmail.com> wrote:
frace is a factor as well. I still get the same error message after dropping (0 + frace | type) part. How can I do the resealing parameters? On Thu, Jul 19, 2018 at 2:33 PM, Ben Bolker <bbolker at gmail.com> wrote:
what is frace? This is a relatively rare error message. It usually indicates a strongly unbalanced/unstable model for some reason. Have you tried rescaling parameters? Do simpler versions of the model work? On Thu, Jul 19, 2018 at 3:15 PM Ahreum Maeng <amaengwork at gmail.com> wrote:
Hello,
I got a following error message while running a MLM using lme4 package.
Error in fn(x, ...) : Downdated VtV is not positive definite
my model was as following:
out <- lmer(situ ~ cult*change + (change || id) + (0 + frace | type), data
= tidy.total, REML=FALSE)
where
situ: numeric
change: numeric
cult: factor (coded in 1 and -1)
How could I fix this issue?
Thanks a lot,
Ahreum
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-- -------------------------------- Ahreum Maeng Assistant Professor in Marketing KU School of Business University of Kansas 1654 Naismith Dr. #2183 Lawrence, KS 66045 https://sites.google.com/site/ahreummaeng1/research ----------------------------------
-- -------------------------------- Ahreum Maeng Assistant Professor in Marketing KU School of Business University of Kansas 1654 Naismith Dr. #2183 Lawrence, KS 66045 https://sites.google.com/site/ahreummaeng1/research ----------------------------------