Dolfin in python: How do i read data from a .pvd file and plot it?

If you just want plotting, open it in Paraview:
http://paraview.org/

Martin

On 10 February 2012 15:20, Jens V Christiansen
<email address hidden> wrote:
> New question #187403 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/187403
>
> Hi,
>
> How do i read data from a .pvd file and plot it?
>
> Say for instance the velocity solution to the stokes-iterative problem:
>
>
> from dolfin import *
>
> # Load mesh and subdomains
> mesh = UnitCube(16, 16, 16)
>
> # Define function spaces
> V = VectorFunctionSpace(mesh, "CG", 2)
> Q = FunctionSpace(mesh, "CG", 1)
> W = V * Q
>
> (u, p) = TrialFunctions(W)
>
> # Load solution in VTK format
> File("velocity.pvd") >> u
> pfile_pvd = File("pressure.pvd")
> pfile_pvd >> p
>
> # Plot solution
> plot(u)
> plot(p)
> interactive()
> -----------------------
>
> I get the following error:
>
> Traceback (most recent call last):
>  File "plot_solution.py", line 20, in <module>
>    File("velocity.pvd") >> u
> TypeError: in method 'File___rshift__', argument 2 of type 'dolfin::FunctionPlotData &'
>
>
>
>
> --
> You received this question notification because you are a member of
> DOLFIN Team, which is an answer contact for DOLFIN.

*.pvd files are paraview data format, so you can import them into
Paraview http://www.paraview.org/

The plotting facilities in Paraview are far advanced of those
available in Dolfin, so I would highly recommend getting to grips with
it (most things are point-and-click).

If you really want to do what you've asked I guess its possible to
save the underlying numpy array with the nodal unknowns of u and p and
reinitialise a fresh Function object in your plotting script with the
numpy array loaded from a file, but I've never tried to do this myself
so I don't know the exact steps.

Jack

On 10 February 2012 14:20, Jens V Christiansen
<email address hidden> wrote:
> New question #187403 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/187403
>
> Hi,
>
> How do i read data from a .pvd file and plot it?
>
> Say for instance the velocity solution to the stokes-iterative problem:
>
>
> from dolfin import *
>
> # Load mesh and subdomains
> mesh = UnitCube(16, 16, 16)
>
> # Define function spaces
> V = VectorFunctionSpace(mesh, "CG", 2)
> Q = FunctionSpace(mesh, "CG", 1)
> W = V * Q
>
> (u, p) = TrialFunctions(W)
>
> # Load solution in VTK format
> File("velocity.pvd") >> u
> pfile_pvd = File("pressure.pvd")
> pfile_pvd >> p
>
> # Plot solution
> plot(u)
> plot(p)
> interactive()
> -----------------------
>
> I get the following error:
>
> Traceback (most recent call last):
>  File "plot_solution.py", line 20, in <module>
>    File("velocity.pvd") >> u
> TypeError: in method 'File___rshift__', argument 2 of type 'dolfin::FunctionPlotData &'
>
>
>
>
> --
> You received this question notification because you are a member of
> DOLFIN Team, which is an answer contact for DOLFIN.

Thanks! Paraview is the way to go.