remove outliers from a circumference

hi guys.. I have a series of points, those points generates a sort of circumference/ellipse in the 3d space ( intersection between a shpere and a cone).. i want to get rid of the outliers....I've tried using rmoutliers, but nothing.. can you help me?

Answer 1

[darova]

Here is an idea:

x0 = mean(x);                          % Choose some center point (maybe approximately)
y0 = mean(y);
[t,r] = cart2pol(x,y);                 % convert your data to polar system
[~,ix] = sort(t);                      % sort your data by angle
tol = 0.4;                             % some tolerance
ix1 = find(diff(r(ix) > tol);          % find values where difference of radius is too big
ind = ix(ix1);                         % indices of outlier points
plot3(x(ind),y(ind),z(ind),'or')

[luca antonioli]

yes, it is a good idea..but how to consider the center of the circumference?

you calculate x0 and y0 but you dont use these points!

[darova]

Opps! Data should be replaced to 'origin'. Try:

[t,r] = cart2pol(x-x0,y-y0);                 % convert your data to polar system