I cannot use interp2 function instead of griddata

I have a dynamic model as a MATLAB script that uses griddata function for interpolation. When I tried to implement the same model in Simulink, the only way I could use griddata was by using Matlab Function Block with coder.extrinsic('griddata') command inside. After that the Simulink model was working fine but when I tried generate a code from that model it was not possible due to griddata does not have the C/C++ Code Generation Capability. After some research, I figured out that I could use interp2 function as an alternative which has the extended capability of C/C++ Code Generation. However, when I tried to use it I got an error says; 'Grid arrays must have NDGRID structure.'

Here, a sample data extracted from my dynamic model is given with griddata and interp2 functions.

clear, clc;

% sample data

x = [1.1390, 1.1069, 1.0868;

0.6763, 0.5188, 0.2399;

0.8110, 0.1311, -0.5368;

1.2953, 0.7618, 0.3221;

1.1390, 1.1069, 1.0868];

y = [0, 0, 0;

0.1640, 0.4879, 0.8118;

0.0000, 0.0000, 0.0000;

-0.1640, -0.4879, -0.8118;

-0.0000, -0.0000, -0.0000];

v = [0, 0, 0;

0.1352, 0.2279, 0.6906;

0.0417, 0, 0.5807;

0, 0.1010, 0.4709;

0, 0, 0];

xq = [0.2000, 0.5950, 0.9900;

0.0000, 0.0000, 0.0000;

-0.2000, -0.5950, -0.9900;

-0.0000, -0.0000, -0.0000;

0.2000, 0.5950, 0.9900];

yq = [0, 0, 0;

0.2000, 0.5950, 0.9900;

0.0000, 0.0000, 0.0000;

-0.2000, -0.5950, -0.9900;

-0.0000, -0.0000, -0.0000];

% griddata function

vq = griddata(x,y,v,xq,yq,'cubic');

% interp2 function

Vq = interp2(x,y,v,xq,yq,'cubic');

I would like to get the same result using either interp2 function or any other function that has the C/C++ Code Generation Capability. Then I would be able to use it for code generation.

[Les Beckham]

If you explain what the purpose of the block is in your Simulink model, perhaps someone can suggest an alternative that would be supported for code generation. Perhaps a table lookup block? What are the block inputs and outputs, for example. I don't see anything "dynamic" in the example code you have shown.

The responses in this answer suggest that scatteredInterpolant might be an option:

https://www.mathworks.com/matlabcentral/answers/1945854-i-cannot-use-interp2-as-matlab-tells-me-my-grid-arrays-do-not-have-an-ndgrid-structure-but-i-am-sti

[Stephen23]

"I cannot use interp2 function instead of griddata"

Correct: your data are not gridded, therefore you cannot use INTERP2.

Select a scattered interpolant: https://www.mathworks.com/help/matlab/math/overview-of-interpolation-techniques.html

[Serhat Sarihan]

Thank you for your responses. I will try to solve this issue by the help of those links you've shared.

Note: The code I shared is a dummy script for generating data to a sample point of my dynamic model. The original code is old and written by another person. I was trying to make use of it to create a dynamic model and made some modifications to it for that purpose. This was the part I did not understand.

Answer 1

[Matt J]

scatteredInterpolant is supported for Code Generation as of R2024b, so if you can upgrade from R2019b, that might sove it.

[Serhat Sarihan]

Thank you for this advise Matt.

After making some adjustments on my model to use scatteredInterpolant properly I should upgrade my Matlab version as you suggest.

[Matt J]

You're welcome, but if this resolves your question please Accept-click the answer.