Evaluation of derivatives functions

[dansand]

Example:

sr -= (stokes.div_u/mesh.dim)*eye(mesh.dim)  
inv2 = sr[0,0]**2 + sr[0,1]**2 + sr[1,0]**2 + sr[1,1]**2   
inv2 = 1/2.*inv2
strainRate_2ndInvariant = sqrt(inv2)

uw.function.evaluate(strainRate_2ndInvariant, mesh.data)

RuntimeError: Derivatives functions are not handled yet unfortunately.

This is a known limitation as the error message makes clear. But for experimentation it would (really) useful to be able to view things like the strain rate.

[lmoresi]

I second this - we have variable interpolation (rbf only suitable for fields), we have projection (works for anything but maps to nodes), and we have this half-working function_evaluation that ought to be the most general but is hopelessly limited.