Defining Model Settings Using External Data File
To use tabulated data from files in a model, use the interpolation function available under the Global Definitions node or the Definitions node of the model.
To add an interpolation function under the Global Definitions node, enter:
model.func.create(<functag>, 'Interpolation')
If you have several model nodes in your model and you want to attach it to the specified component node <ctag>, enter:
model.component(<ctag>).func.create(<functag>, 'Interpolation')
where <ctag> is the tag of the model node to attach the interpolation function.
Then you can interpolate data specified by a table inside the function (default), or specified in an external file.
When using an interpolation table, set the interpolation data for each row of the table with the commands:
func.setIndex('table', <t_value>, <i>, 1)
func.setIndex('table', <ft_value>, <i>, 2)
where func is a link to a function node and <t_value> is the interpolation parameter value and <ft_value> is the function value. <i> is the index (0-based) in the interpolation table. If the number of rows is large then it takes a long time to create the table element by element. Instead store all the data as a cell array of strings and set the values all at once:
func.set('table', data)
To use an external file change the source for the interpolation and specify the file, where filename is the name (including the path) of the data file:
func.set('source', 'file')
func.set('filename', <filename>)
Several interpolation methods are available. Choose the one to use with the command:
func.set('interp', method)
The string method can be set as one of the following alternatives:
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'neighbor', for interpolation according to the nearest neighbor method,
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'linear', for linear interpolation method,
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'cubicspline', for cubic spline interpolation method, or
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'piecewisecubic', piecewise cubic interpolation method.
You can also decide how to handle parameter values outside the range of the input data by selecting an extrapolation method:
func.set('extrap', method)
The string method can be one of these values:
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'const', to use a constant value outside the interpolation data,
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'linear', for linear extrapolation method,
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'nearestfunction', to use the nearest function as extrapolation method, or
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'value', to use a specific value outside the interpolation data.
model.func() in the COMSOL Multiphysics Programming Reference Manual or type at the MATLAB prompt: mphdoc(model.func).