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February 23, 2010 8:22pm UTC in response to Christian Renneke

Re: Interpolation .txt-File Format Error: 9048

Hi

are you sure it is not your function name "test()", I beleive this is a reserved name for COMSOL "test" function for weak variables

Good luck
Ivar

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March 1, 2010 8:46am UTC in response to Christian Renneke

Re: Interpolation .txt-File Format Error: 9048

I'm back at work on this topic and am still searching for a solution. I tried different names as well and still get the same error message when i press the "update model" button:
"Exception:
com.femlab.jni.FlNativeException: Format of data file is not correct
Messages:
Format of data file is not correct

Stack trace:
at interputil.cpp, row 636, ()
at com.femlab.xmesh.Xmesh.addElems(Native Method)
at com.femlab.xmesh.Xmesh.addElems(Unknown Source)
at com.femlab.commands.MeshExtendCommand.c(Unknown Source)
at com.femlab.commands.MeshExtendCommand.s(Unknown Source)
at com.femlab.commands.MeshExtendCommand.evalOnServer(Unknown Source)
at com.femlab.commands.FlCommand.runServerCode(Unknown Source)
at com.femlab.server.ServerProxy.eval(Unknown Source)
at com.femlab.commands.FlCommand.a(Unknown Source)
at com.femlab.commands.FlCommand.eval(Unknown Source)
at com.femlab.commands.a.a(Unknown Source)
at com.femlab.util.CoreUtil.meshExtend(Unknown Source)
at com.femlab.api.client.Solver.solve(Unknown Source)
at com.femlab.api.client.SolveModel.solveNow(Unknown Source)
at com.femlab.api.client.SolveModel.solveNow(Unknown Source)
at com.femlab.api.client.ah.a(Unknown Source)
at com.femlab.gui.FlProgressThread.run(Unknown Source)
at com.femlab.util.i.run(Unknown Source)
at com.femlab.util.aa.run(Unknown Source)
"
Is there a more easy way to test my data import?

Thanks, Christian

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March 2, 2010 10:36pm UTC in response to Christian Renneke

Re: Interpolation .txt-File Format Error: 9048

Is there an easy way to generate a plot of a function defined in this way, to confirm that the data file is imported and interpretated correctly?

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March 3, 2010 9:13am UTC in response to Ivar K

Re: Interpolation .txt-File Format Error: 9048

The 'plot...' button exsists (at least in my version) only for analytic functions. But after solving you can plot it with: Postprocessing -> Domain plot parameters -> surface: functionname.

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March 5, 2010 10:09am UTC in response to Ivar K

Re: Interpolation .txt-File Format Error: 9048

I would like to import many functions to COMSOL an easy way.


Therefore I made the following experiment
to create a function interpfun1(x,y)

export the fem structure to matlab.

Run the following code:

x=[0 1 2 3]
y=[0 1 2 3]
data=[1.1 1.4 1.7 1.9; 1.6 1.7 1.8 1.9; 1.4 1.3 1.2 1.1; 1.1 1.2 1.3 1.4]

fem.functions{1}.type = 'interp';
fem.functions{1}.name = 'interpfun1';
fem.functions{1}.method = ''linear';
fem.functions{1}.extmethod = 'linear';
fem.functions{1}.x = x
fem.functions{1}.y = y
fem.functions{1}.data = data

Then import the fem structure again.
Unfortunately I get the following error message:

"Not a cell array.
-Field: fem.functions{1}.x"

What is wrong?

Is this method generally the the right one?

(I am very new to Matlab and COMSOL)

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March 5, 2010 1:01pm UTC in response to Christian Renneke

Re: Interpolation .txt-File Format Error: 9048

Some help with this data conversion will be much appreciated.

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March 5, 2010 6:23pm UTC in response to Ivar K

Re: Interpolation .txt-File Format Error: 9048

So it will be easier to create these data formats with Maple

for automated interpolation function import in COMSOL.

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March 5, 2010 9:22pm UTC in response to Ivar K

Re: Interpolation .txt-File Format Error: 9048

Hi again

Now to come back to the example of the function defined in matlab: my way in these situations is always to generate an example in the Comsol GUI and then to look at it in Matlab, before I create anything the opposite way, then what I see is that (V3.5a):

the data in fem.functions.x .y and .data are structures with a cell for each number saved in an ascii representation and not an array of numbers, this is probably why COMSOL is not happy.

As ASCII values the expression can be evaluated further by COMSOL, in case it is a full expression with variable names an not just numbers

There are more in the "Variables and Expressions" section of the help file with a few matlab examples too

This is what I get for two simple function defined in the comsol GUI taken from the saved .m file:

% Functions
clear fcns
fcns{1}.type='interp';
fcns{1}.name='tst';
fcns{1}.method='piecewisecubic';
fcns{1}.extmethod='interior';
fcns{1}.x={'1','2','3','4'};
fcns{1}.data={'1','4','9','16'};

fcns{2}.type='piecewise';
fcns{2}.name='tstpcw(x)';
fcns{2}.extmethod='const';
fcns{2}.subtype='general';
fcns{2}.expr={'x^2','x^3'};
fcns{2}.intervals={'0','1','2'};
fcns{2}.complex='false';
fcns{2}.linear='false';
fem.functions = fcns;


for 2 variable functions the data must be sorted along the formatof a "meshgrid" call see help file:

here is an excerb of my help file, but I agree there is nothing stated about the special format of the .x, .y, .z not .data
-------------------------
To retrieve data from MATLAB, create a structure on the command line with the fields x, y (optional), z (optional), data, and elem (optional). For structured data, x, y, and z are vectors specifying the grid, and data is a multidimensional array of the same format as produced by the function call [xx,yy,zz] = meshgrid(x,y,z);. For example, to define the function f(x, y, z) = xysin(z) on a unit-cube grid and prepare it for export to COMSOL Multiphysics, type the following on the MATLAB command line:

x = 0:0.1:1; y = 0:0.1:1; z = 0:0.1:1;
[xx,yy,zz] = meshgrid(x,y,z);
data = xx.*yy.*sin(zz);
f.x = x; f.y = y; f.z = z; f.data = data;

----------------------------------------

Hope this helps further on the way

Good luck
Ivar

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March 10, 2010 6:38am UTC in response to Jens Jensen

Re: Interpolation .txt-File Format Error: 9048

Hi

my only comment, when you have usefull suggestions, document them by explaining why etc and send them to Comsol Support so that they canbe introduced into the improvements for next version. I'm doing it regularly and it works :)

Good luck
Ivar

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