MATLAB: Data is not valid NDGRID format.

4-dinterpnmeshndgrid

I would like to know what does it mean "Data is not valid NDGRID format" when I try to use interpn() function to interpolate a function from four variables. I've already checked, a dozen times, my matrixes dimensions. Which one of them agrees in size (4D – 2x11x4x3). Besides, there is no way I can use ndgrid() function to create the mesh, in this case I did this mannualy.
If I have all the function values for which one of the variables, why this error appears?
Thanks in advance,

Best Answer

From the doc for interpn one finds...
"interpn requires that X1,X2,X3,etc. be monotonic and plaid (as if
 they were created using NDGRID).  X1,X2,X3,etc. can be non-uniformly
 spaced."
So, it doesn't matter about the dimension so much, only that the Xn vectors/arrays be monotonic and non-repeating such that they are valid for ndgrid. That you say "there is no way I can use ndgrid() function to create the mesh" pretty much means you can't use interpn to interpolate the data, either (actually, it means it flat out, not just "pretty much" :) ).
You can try some of the other interpolation methods.
Why, specifically, can't you use ndgrid? What is a (smallish) typical subset of the data grid for looksies?
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