how to mark edges from list of nodes...

Question

Hi every one,

I have a list of nodes from my mesh. I d like to mark the edges from a this list.
I m not sure if it is the best away, but if i have one segment and this segment has theirs two nodes from this list. It will be marked.

list=[1,5,6,7] =DATA

How to do it? Is it the best away to do it? Because there will lots of loops to do.

Thanks.

Answer 1

Hi,

so i did not programm the full answer but most of it. What you want should be something like this:

    from dolfin import*
    import numpy as np

    p1 = Point(0.0,0.0)
    p2 = Point(40e-3,40e-3)

    mesh_density = 5

    mesh = RectangleMesh(p1,p2, mesh_density, mesh_density)

    edge = EdgeFunction("size_t", mesh)
    edge.set_all(0)

    for e in edges(mesh):
           owned_vertices = np.sort(e.entities(0))
           edge_number = e.index()
           if (here you need to add something now, if owned_vertices (both) are on your list):
                    edge[edge_number]=42

     plot(edge)    

Kind regards

Johann

Comments

I forgot to mention, i assumed you want it in 2D, i did not test it for 3D.

---

Thanks. I am looking for it now.

I did one simple exemplo with 2D mesh to see (mesh_density =2). I d like to mark 2 edges. Then I have a list of this nodes.

List of nodes from mesh:

In this exemplo:

from dolfin import*
import numpy as np
Lc=1E-3
p1 = Point(0.0,0.0)
p2 = Point(Lc,Lc)

mesh=RectangleMesh(p1, p2, 2, 2, "left")
nodes=MeshFunction("size_t", mesh, 0)
boundaries = FacetFunctionSizet(mesh, 1)

#the list of nodes:
list=[3,4,7]

There are 2 segments that contain this nodes [3 and 4] the first one and the second one node 4 and node 7

How can i mark my "FacetFunctionSizet"?

I will try using what you did...

thanks!!!

I did:

   B = Function(V)
   a = np.zeros(np.shape(nodes))
   DATA=[3,4,7]
   for i in DATA:
      a[i]=1.

   dofmap = dof_to_vertex_map(V)
   amod = a[dofmap]
   B.vector()[:] = amod

   C=Function(V)
   C.vector()[:]=a
   plot(B)
   plot(C)

B is totally different than C bc dofmap...

The problem is I have the nodes but not the list of segments... and it is reagroup for dofmap

---

Thanks for help me .. but i think it the list is regroup for dof map...