Test whether a fit is singular or reduced-rank

Follows lme4::isSingular(): a fit is singular when any covariance parameter with a lower bound of zero (a diagonal element of a relative covariance factor, getME(x, "lower") == 0) is below tol. Works for lmm() and glmm() fits. lme4::isSingular() is a plain function, so it cannot dispatch on mixeff fits; call is_singular() instead. Fits without a stored theta map (very old serialized objects) fall back to the engine's fit-status and effective-covariance labels.

Usage

is_singular(x, tol = 1e-04, ...)

# S3 method for class 'mm_lmm'
is_singular(x, tol = 1e-04, ...)

# S3 method for class 'mm_glmm'
is_singular(x, tol = 1e-04, ...)

Arguments

x

A fitted mm_lmm or mm_glmm.

tol

Tolerance on the zero-bounded theta values (default 1e-4, as in lme4).

...

Reserved for future methods.

Value

A length-one logical value.