Reports the groups that frm_ode() could not solve on its most
recent call, and whose rows therefore hold the penalty value rather
than a solution. frm_ode() also warns when that happens; this
function is for reading the record afterwards, for example after a
predict() whose warnings were suppressed.
Value
NULL when the last call solved every group. Otherwise a
list with groups (the labels that failed), n_groups (how many
groups the call had), penalty (the value written into their
rows), and when.
Details
The record covers the last call only, from anywhere: a fit, a
predict(), or a direct call. It is reset by every frm_ode() call,
so a clean call clears it. See the "Failed solves" section of
frm_ode() for why a failure during fitting usually cannot be
recorded at all.