print coordinate of boundary seperately i.e., left boundary

Question

Hi,

I want to print coordinates of the separate boundary such as left, right, top and bottom,

I have tried doing this but this will give all the coordinates on the boundary. Thanks in advance.

from dolfin import *
mesh = UnitSquareMesh(2,2)

It_mesh = vertices(mesh)
for c in It_mesh:
     print (c.point().x())

Answer 1

Would this work for you:

from dolfin import *
mesh = UnitSquareMesh(2,2)

class Boundary(SubDomain):
        def inside(self, x, on_boundary):
                tol = 1E-14
                return on_boundary and near(x[0], 0, tol)

boundary = Boundary()
ff = FacetFunction('size_t',mesh)
boundary.mark(ff,1)

It_mesh = SubsetIterator(ff, 1)

for c in It_mesh:
     print (c.midpoint().x(), c.midpoint().y())

Comments

it is working but it is giving mid point of the nodes. I need x and y coordinates.

thanks for the help. :)

---

Ah, right, this iterates over the facets.
So maybe just play around with vertices() now, something like:

for f in It_mesh:

    for v in vertices(f):

        print v.midpoint().x(), v.midpoint().y()

This will give you overlapping vertices, but that could be fixed

---

Thanks it really helps