interpolateSolution for a system of time dependent PDEs

Hello and sorry again if the question is silly.

I have a system of 2 PDEs. I solved them using the command:

res=solvepde(modelTwoDomain,tlist);

Solution in the nodes is:

sol=res.NodalSolution;

So far so good. Now is when I think I am being silly.

I want to interpolate the solution for a given point x=1.24 and y=1.22. They belong to the geometry of the model and I try to use interpolate solution.

I use: uxy = interpolateSolution(res,1.24,1.22);

and the following error comes up:

Error using pde.PDEResults.interpolateSolutionInternal

Incorrect number of input arguments.

Error in pde.TimeDependentResults/interpolateSolution (line 82)

uintrp = pde.PDEResults.interpolateSolutionInternal(obj,varargin{:});

What am I doing wrong?

Thanks

Answer 1

[Torsten]

For a time-dependent solution, you must additionally specify the index of the output time for which you want to interpolate:

uintrp = interpolateSolution(___,iT) returns the interpolated values of the solution to the time-dependent or eigenvalue equation or system of such equations at times or modal indices iT. For a system of time-dependent or eigenvalue equations, specify both time/modal indices iT and equation indices iU

[Jorge Garcia Garcia]

Thanks Torsted!

I am trying as you suggested (and I apologise as I am still quite new with Matlab, so I am sure I am doing something wrong)

If I write in command windows:

uintrp = interpolateSolution(res,1.24,1.22,5)

I should be solving for x=1.24; y=1.22 and time index 5

That gives the following error:

Error using pde.PDEResults.validatePointsMatrix

Query point matrix does not contain coordinates of 2-D space in required format.

Error using pde.PDEResults.validatePointsMatrix

Query point matrix does not contain coordinates of 2-D space in required format.

I have also try to pass position as vector (both as colum and row vector) and then the error is:

uintrp = interpolateSolution(res,Q,5)

Error using pde.PDEResults.interpolateSolutionInternal

Incorrect number of input arguments.

Error in pde.TimeDependentResults/interpolateSolution (line 82)

uintrp = pde.PDEResults.interpolateSolutionInternal(obj,varargin{:});

sorry about this, I admit I am a bit lost with Matlab

[Torsten]

Read the documentation.

You say you solve two PDEs. Thus your call to "interpolateSolution" must have 5 arguments, not 4.

[Jorge Garcia Garcia]

Thanks Torsten, for someone like me with not a lot of training in matlab, documentation is quite hard to understand. It is true that passing a fith argument, it returns a value. I will try to understand what is the meaning of the 5 arguments. Thanks again.

[Torsten]

The fourth is the index of the PDE, the fifth is the time index.

Look at the example

Interpolate Time-Dependent System

under

https://de.mathworks.com/help/pde/ug/pde.stationaryresults.interpolatesolution.html

[Jorge Garcia Garcia]

Thanks! you really saved my sanity!