Interp2/Scatterinterp unstructured Data don't work!

Hi MathworKS community,

i hava a set of data that i can plot like the picture below , as you see it dosen't cover all the area

so when i use interp2 to find the value of Z inside the contour i get this error 'Input grid is not a valid MESHGRID.'

i have an idea : fill the empty area with Nan, but it's a little bit confusig for me.

any solution?

contourf(X,Y,Z)
colormap jet;
interp2(X,Y,Z,3000,50)  %for example i want to interpolate at X=3000 and Y=50

Answer 1

[Star Strider]

Use the griddata function instead.

Try this:

Xm = load('X.mat');
X = Xm.Mecanical_Speed;
Ym = load('Y.mat');
Y = Ym.Torque_max_Matrice;
Zm = load('Z.mat');
Z = Zm.Efficiency;

Xi = 3000;
Yi = 50;
Zi = griddata(X,Y,Z,Xi,Yi)  %for example i want to interpolate at X=3000 and Y=50

figure
contourf(X,Y,Z)
hold on
plot3(Xi, Yi, Zi, '+k', 'MarkerSize',20)
hold off
colormap jet;
text(Xi,Yi,Zi, sprintf('    \\leftarrow (%3d, %2d, %.3f)', Xi,Yi,Zi), 'VerticalAlignment','middle','HorizontalAlignment','left', 'FontWeight','bold')

producing:

.

[Meddour Aissam riad]

Thanks a lot MVP! @Star Strider

[Star Strider]

As always, my pleasure!