Problem with Interpolation function involving 2 variables

Hi,

I've tried to use the interp2 function to interpolate 'Zq' coordinates from the raw 'X,Y,Z' data attached in the file here. Interpolation is carried for Xq = -60:60 and Yq = -160:160.

I'm getting an error of this kind when I run the program.

" Error using griddedInterpolant

The grid vectors must be strictly monotonically increasing"

Is there a way to find the interpolation for such data?

[KSSV]

Use meshgrid for Xq and Yq.

Answer 1

[Walter Roberson]

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/727494/xyz.xlsx';
T = readtable(filename);
F = scatteredInterpolant(T.X, T.Y, T.Z);
Xq = -60:60;
Yq = -160:160;
[XQ, YQ] = meshgrid(Xq, Yq);
ZQ = F(XQ, YQ);

surf(XQ, YQ, ZQ, 'edgecolor', 'none');
xlabel('x'); ylabel('y'); zlabel('z')

[Sangani Prithvi]

Thank you very much.

Answer 2

[KSSV]

T = readtable('xyz.xlsx') ; 

x = T.X ; y = T.Y ; z = T.Z; 


Xq = -60:60 ;
Yq = -160:160.  ; 
[Xq,Yq] = meshgrid(Xq,Yq) ; 

Zq = griddata(x,y,z,Xq,Yq) ; 

[Sangani Prithvi]

Thanks for the answer.

I'm getting few NaN values in Zq matrix.

[KSSV]

You will get only where the points lie outside the give data.

[Walter Roberson]

You might want to set an extrapolation method.