How to evaluate a function which is in a SubFunctionSpace?

General
1

Hello everyone:
I am working in fenics 2019.02 on docker . Now, i need someone help me to solve this problem.
I have a SubFunction u which in a mixed functionspace and another function v in a VectorFunctionSpace . How can i do to set u = v.
This is an exanple code

from fenics import *
import numpy as np
import matplotlib.pyplot as plt
from mshr import *

#create mesh
domain = Rectangle(Point(0.0, 0.0), Point(10.0, 1.0))
mesh = generate_mesh(domain, 100)
x = SpatialCoordinate(mesh)

u_elem = VectorElement("P", mesh.ufl_cell(), 2)
p_elem = FiniteElement("P", mesh.ufl_cell(), 1)
elem = MixedElement([u_elem, p_elem])
V = FunctionSpace(mesh, elem)

V_disp = VectorFunctionSpace(mesh, "P", 2)

up = Function(V)
u, p = split(up)
v = project(as_vector((x[0], x[1])), V_disp)

u.vector()[:] = v.vector()

how to let u = v and u is always in the mixed space , v is always in the VectorFunctionSpace?

Thanks!

2

You can use the function assigner, see Usage of FunctionAssigner - #2 by dokken