Hello everyone,

1- How I can find the minimum eigenvalue ?

2- How I can determine the eigenvectors correspond to the minimum eigenvalue ?

3 -How I can plot the eigenvectors ?

Thank you for your time and consideration.

Cordially

Hello everyone,

1- How I can find the minimum eigenvalue ?

2- How I can determine the eigenvectors correspond to the minimum eigenvalue ?

3 -How I can plot the eigenvectors ?

Thank you for your time and consideration.

Cordially

Consider the following example:

```
from dolfin import *
# Set up some simple variational form for illustration:
mesh = UnitIntervalMesh(100)
V = FunctionSpace(mesh,"CG",1)
u = TrialFunction(V)
v = TestFunction(V)
a = dot(grad(u),grad(v))*dx + u*v*dx
# Must assemble form to a PETScMatrix:
A = PETScMatrix()
assemble(a,tensor=A)
# Create eigenvalue solver:
eigenSolver = SLEPcEigenSolver(A)
# Configure solver to get the smallest eigenvalues first:
eigenSolver.parameters["spectrum"]="smallest magnitude"
# Solve for the N smallest eigenvalues:
N = 5
eigenSolver.solve(N)
from matplotlib import pyplot as plt
for i in range(0,N):
# The smallest eigenpair is the first (0-th) one:
r, c, rx, cx = eigenSolver.get_eigenpair(i)
# Turn the eigenvector into a Function:
rx_func = Function(V)
rx_func.vector()[:] = rx
# Function can be plotted as usual:
plot(rx_func)
plt.autoscale()
plt.show()
```

1 Like

Thank you for helping me with your detailed answer.