Hi Francis, There are two things here. The first is the proximate cause of your exception. If f is a FunctionSpace then it doesn't have an interpolate method. Instead, you would call the interpolate function: c = interpolate(MyExpression(), f). However, creating a subclass of Expression is not the best way to solve this problem. Instead you should interpolate a UFL expression: x = SpatialCoordinate(f.mesh()) c = interpolate(conditional(le(x[0], 0.5), 1.0, 0.0), f) Regards, David On Sun, 26 Feb 2017 at 22:06 Francis Poulin <fpoulin@uwaterloo.ca> wrote:
Hello,
I am trying to define an expression piecewise and see that I need to do that by defining a class. Below is something that I tried, building on what I read, but it has an error, see below.
class MyExpression(Expression): def eval(self, value, x): if x[0] <= 0.5: value[0] = 1.0 else: value[0] = 0.0
def value_shape(self): return (1,)
f.interpolate(MyExpression())
It fails with the following error:
AttributeError: 'FunctionSpace' object has no attribute 'interpolate'
Can someone maybe point me in the right direction on how to do tis properly?
Cheers, Francis
------------------ Francis Poulin Associate Professor Department of Applied Mathematics University of Waterloo
email: fpoulin@uwaterloo.ca Web: https://uwaterloo.ca/poulin-research-group/ Telephone: +1 519 888 4567 x32637 <(519)%20888-4567>
-- Dr David Ham Department of Mathematics Imperial College London