Hi everyone,

I'm trying to vectorize an application of lda to each 2D slice of a 3D
array, but am running into trouble:  It seems there are quite a few 2D
slices that trigger either the "variables are collinear" warning, or worse,
trigger a "variable appears to be constant within groups" error and fails
(i.e., ceases computation rather than skips bad slice).

There are cases where neither warning is literally true, so I expect the
warning and error must be triggered in a neighborhood of collinearity and
within-group-constancy, and I would like to be able to remove the offending
slice in advance.   Does anyone know where I can find the explicit tests
that are used for these?

Thanks in advance for any light you can help shed on this question.

Best,
David

P.S.  The 3D array has roughly 40K 2D slices, so inspection is not an
option!

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