# evaluate boundary integrals

Asked by
James Lai

Hi,

After obtaining my solution using dolfin through python

problem = VariationalProb

U = problem.solve()

is there any way to integrate the solution over a given boundary edge?

Lets say I set up subdomains, then if I want to integrate n dot u over subdomain 1, I tried

ds_in = Measure(

n_in = Constant((-1,0))

val = Integral(

It seems like when i do this, val is a not a number, but a Integral type. Is there any way to evaluate this integral and get a number out of it ?

Thanks

## Question information

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- Status:
- Solved

- For:
- DOLFIN Edit question

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- Solved by:
- Johan Hake

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