I know the coordinates of several scattered points in space, how can I fit them to a sphere?
3 views (last 30 days)
Show older comments
I already know the coordinates (x,y,z) of several scattered points on a sphere in space, and my goal is to fit a sphere and get the radius. I think I just need to bring their coordinates into the code I found. I would like to ask how to bring in the coordinates of these points?
function [r,a,b,c] = sphereFit(data)
xx = data(:,1);
yy = data(:,2);
zz = data(:,3);
AA = [-2*xx, -2*yy , -2*zz , ones(size(xx))];
BB = [ -(xx.^2+yy.^2+zz.^2)];
YY = mldivide(AA,BB); %Trying to solve AA*YY = BB
a = YY(1);
b = YY(2);
c = YY(3);
D = YY(4); % D^2 = a^2 + b^2 + c^2 -r^2(where a,b,c are centers)
r = sqrt((a^2+b^2+c^2)-D);
The second code:
function [Center,Radius] = sphereFit(X)
A=[mean(X(:,1).*(X(:,1)-mean(X(:,1)))), ...
2*mean(X(:,1).*(X(:,2)-mean(X(:,2)))), ...
2*mean(X(:,1).*(X(:,3)-mean(X(:,3)))); ...
0, ...
mean(X(:,2).*(X(:,2)-mean(X(:,2)))), ...
2*mean(X(:,2).*(X(:,3)-mean(X(:,3)))); ...
0, ...
0, ...
mean(X(:,3).*(X(:,3)-mean(X(:,3))))];
A=A+A.';
B=[mean((X(:,1).^2+X(:,2).^2+X(:,3).^2).*(X(:,1)-mean(X(:,1))));...
mean((X(:,1).^2+X(:,2).^2+X(:,3).^2).*(X(:,2)-mean(X(:,2))));...
mean((X(:,1).^2+X(:,2).^2+X(:,3).^2).*(X(:,3)-mean(X(:,3))))];
Center=(A\B).';
Radius=sqrt(mean(sum([X(:,1)-Center(1),X(:,2)-Center(2),X(:,3)-Center(3)].^2,2)));
Which code should I choose and apply correctly?
Accepted Answer
Image Analyst
on 4 Feb 2023
Edited: Image Analyst
on 4 Feb 2023
It looks like the input data for both functions is an N-by-3 matrix.
0 Comments
More Answers (0)
See Also
Categories
Find more on Scatter Plots in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!