Hi everyone,

I’m using FEniCS 2019.1.0 and I’m trying to plot the solution of the Poisson equation using Matplotlib, instead of the built-in FEniCS method. The following lecture plotting, published in 2017, shows an example in which the Cahn-Hilliard tutorial is modified with the following lines

```
from matplotlib import pyplot
parameters [ " plotting_backend " ] = " matplotlib "
```

and the output is what one would expect -

Conversely, if I try adding the same lines to my program (again, using FEniCS 2019.1.0), I get the following error message printed to the console:

```
File ~/anaconda3/envs/fenicsproject/lib/python3.12/site-packages/spyder_kernels/py3compat.py:356 in compat_exec
exec(code, globals, locals)
File ~/cronin_group_research/Active-Particles/chemotaxis/autochemotaxis/single_particle/apply_exact_delta/untitled0.py:31
fe.parameters ["plotting_backend"] = "matplotlib"
RuntimeError: Parameter plotting_backend not found in Parameters object
```

Is there any way I can make this work? Find below the program I’m trying to run

```
import fenics as fe
import mshr as msh
from matplotlib import pyplot
fe.parameters["plotting_backend"] = "matplotlib"
domain = msh.Circle(fe.Point(0,0), 1)
mesh = msh.generate_mesh(domain, 64)
V = fe.FunctionSpace(mesh, "P", 1)
u_D = fe.Expression("0", degree = 2)
def boundary(x, on_boundary):
return on_boundary
bc = fe.DirichletBC(V, u_D, boundary)
u = fe.TrialFunction(V)
v = fe.TestFunction(V)
f = fe.Constant(0)
a = fe.dot( fe.grad(u), fe.grad(v) )*fe.dx
L = f*v*fe.dx
u = fe.Function(V)
assembler = fe.SystemAssembler(a, L, bc)
solver = fe.LUSolver("mumps")
A = fe.Matrix()
solver.set_operator(A)
assembler.assemble(A)
b = fe.assemble(L)
delta = fe.PointSource(V, fe.Point(0,0), 1)
delta.apply(b)
bc.apply(b)
fe.solve(A, u.vector(), b)
p = fe.plot(u)
p.set_cmap("viridis")
```