Dan Piponi on Nostr: We have derivatives, and nth derivatives, and fractional derivatives, and at a ...

We have derivatives, and nth derivatives, and fractional derivatives, and at a stretch derivatives of complex order, but what about the Ath derivative where A is a matrix?

https://ajms.ksu.edu.sa/sites/ajms.ksu.edu.sa/files/imce_images/2._g._r._miller_and_a._b._thaheem.pdf

(Annoyed with myself for not thinking of this - even if I can't imagine an application.)