Plot function on IntervalMesh causes Segmentation Fault

Question

I'm having some difficulty plotting a function on an IntervalMesh. The result produces a Segmentation Fault. I am using dolfin version 1.5.

import dolfin as df
mesh = df.IntervalMesh(100, -20, 20)
fs = df.VectorFunctionSpace(mesh, “CG”, 1, 3)
f = df.Function(fs)
f.assign(df.Constant([0, 0, 1]))
df.plot(f)

Thanks in advance,
-- Mark Vousden

Answer 1

Hi,

I think plot(f) can't work because f is a vector valued function, you should also give the index of f you want to plot e.g f[2], which will return the constant function equal to 1 on the interval:

import dolfin as df
mesh = df.IntervalMesh(100, -20, 20)
fs = df.VectorFunctionSpace(mesh, 'CG', 1, 3)
f = df.Function(fs)
f.assign(df.Constant([0, 0, 1]))
df.plot(f[2])

Is that what you wanted?

Comments

Perhaps I should elaborate - I would like the plot to show vectors, similar to what would happen if you used

mesh = df.RectangleMesh(-10, -10, 10, 10, 10, 10)

in place of the IntervalMesh. I realise I could combine three seperate plots of each component, but I'm looking for the vector display in this case. Thanks for your response though!

---

Unfortunately, I'm facing the same problem as yours. The plot command can display vector valued functions thanks to the mode="glyphs" but it seems that it doesn't work on interval meshes. Using the glyphs mode works fine on a square mesh though but something lacks with unidimensional domains...

import dolfin as df
mesh1 = df.UnitSquareMesh(10,10)
mesh2 = df.UnitIntervalMesh(10)
fs1 = df.VectorFunctionSpace(mesh1, 'CG', 1, 3)
fs2 = df.VectorFunctionSpace(mesh2, 'CG', 1, 3)
f1 = df.Function(fs1)
f2 = df.Function(fs2)
f1.assign(df.Constant([0, 0, 1]))
f2.assign(df.Constant([0, 0, 1]))
df.plot(f1,mode="glyphs") #Works
df.plot(f2,mode="glyphs") #Crashes