# How can I get the equation of 3D interpolation?

3 views (last 30 days)
Izan Segarra on 5 Mar 2019
Edited: Matt J on 5 Mar 2019
I'm trying to get the equation of 3D interpolation but i don't know how to do it. ¿How can I get the equation?
Currently I'm getting the values putting F(x,y) in the command window.
x = [470;470;470; 1000; 1000; 1000;];
y = [1;2;3; 1;2;3];
z = [-2.68;-0.98;-0.55;-1.42;0.36;0.8];
scatter3(x,y,z)
F = scatteredInterpolant(x,y,z);
[xq,yq] = meshgrid(470:1000,1:3);
vq1 = F(xq,yq);
plot3(x,y,z,'mo')
hold on
mesh(xq,yq,vq1)
legend('Sample Points','Interpolated Surface','Location','NorthWest') Izan Segarra on 5 Mar 2019
I am making some measurements with differential probes. The results that we are obtaining are generating a lot of error of noise of the electrical installation. Then a study of these results has been made and it is possible to make a compensation to eliminate the noise, but it is necessary to interpolate all the obtained measurements and find an equation for its correction.
I have 4 data vectors:
• Current vector = [1 2 3]
• Impezanze vector = [470 1000]
• Frequency vector = [8 9 10 11 12 15 16]
• Error vector
The error vector contains the error for each impedance at each frequency and for each current, so I need to perform a 4D interpolation and get the equation to correct the measurement error.
I had started with a 3D interpolation and 6 points to understand how to perform the process. Could you help me get the equation?

Matt J on 5 Mar 2019
Edited: Matt J on 5 Mar 2019
I think you want griddedInterpolant instead:
F=griddedInterpolant({current,impedance,frequency}, Error);
Now just use it to evaluate the error at any combination of current, impedance, and frequency of interest,
error_q=F(current_q,impedance_q,frequency_q);
You do not need to fit an equation to your original data.

darova on 5 Mar 2019
Try interp2 or fit
Izan Segarra on 5 Mar 2019
I will try to use fit. Thanks you!

### Categories

Find more on Interpolation in Help Center and File Exchange

R2018b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!