the same transform requested along multiple axes to consistently invoke a 6D version

[karlmsmith]

Reported by steven.c.hankin on 23 May 2016 00:41 UTC
Certain functions, such as AVE and DIN, contain internal logic such that "var[x=@ave,Y=@ave]" actually invokes a multi-dimensional form of the transform. Even for functions that are nominally linear, the presence of missing values creates a non-linearity -- the computation gets a different (better!) result when transforming in multiple axes at once than by transforming each axis in sequence. Other advantages include the role of COS(latitude)in calculations, and the simplicity of understanding what Ferret is calculating.

This behavior should be extended to all transforms. If it is necessary to cut corners in the implementation then
o Smoothers and fillers are in particular cases where the multi-dimensional calculation will give a more useful result;
o simultaneous X and Y analysis is likely to give 80+% of the benefit

Migrated-From: http://dunkel.pmel.noaa.gov/trac/ferret/ticket/2430