fnval error for a struct spline function

Dear all, I have a spline function from a statistical data and I want to present it as 3D and I cant touch this file, when I do this line I have an error and I am wondering how to solve it,

   _ _??? Undefined function or method 'fnval' for input arguments of type 'struct'.

    Error in ==> I at 60
    R = fnval(I,{THETA,PHI,TIME});
   __

I appreciate any idea,

Sareh

Answer 1

[Aditya]

The error message you're encountering in MATLAB indicates that the fnval function is not able to operate on the input provided because it's expecting a different data type than 'struct'. fnval is a function that evaluates a spline at specified points, and it typically expects a spline object as created by MATLAB's Curve Fitting Toolbox or the Spline Toolbox.

Here are some steps you can take to troubleshoot this error:

1. Check the Input Type: Verify the type of the variable I that you are passing to fnval.
2. Check the Spline Representation: If I is supposed to be a spline representation, make sure it was created correctly using the appropriate spline functions (e.g., spapi, spap2, csapi, cscvn, etc.).
3. Examine the Spline Creation: If you cannot modify the file where I is created, examine the process by which I is being generated to ensure it's producing a valid spline object. There may be a step in the process where the spline is being converted to a struct inadvertently.
4. MATLAB Version Compatibility: If the code was written for an older version of MATLAB and you're running it on a newer version, there might be compatibility issues. Check the MATLAB documentation for the version you're using to see if there have been any changes to the spline functions.
5. Alternative Evaluation Function: If I contains the necessary information in a different format, you might need to use a different function for evaluation. For example, if I contains coefficients and knots of a B-spline, you might need to reconstruct the spline using these before evaluation.