MATLAB: Hello everyone, I now have a set of data. I would like to ask how to draw these scattered points in polar coordinates with the centroid point as the center.

in polar coordinatesscattered pointswith the centroid point as the center

It is difficult to draw a closed polar coordinate curve.
load data1.mat
x=data1(:,1);y=data1(:,2);
hold on
plot(centroids(:,1),centroids(:,2),'b*')
[x y]=data1;
[theta,r] = cart2pol(x,y);
% closing the circle
r(end+1) = r(1);
theta(end+1) = theta(1);
% convert to cartesian
[x,y] = pol2cart(theta,r);
% interpolate with parameter t
t = (1:n)';
v = [x,y];
tt = linspace(1,n,100);
X = interp1(t,v,tt,'pchip');
% plot
plot(x,y,'o');
hold on
plot(X(:,1),X(:,2));

Best Answer

hello
this would be my suggestion : 
load data1.mat
load centroids.mat
x=data1(:,1)-centroids(:,1); % centered plot

y=data1(:,2)-centroids(:,2); % centered plot
[theta,r] = cart2pol(x,y);
% closing the circle
r(end+1) = r(1);
theta(end+1) = theta(1);
% sort theta in ascending order
[theta_sorted,ind] = sort(theta);
r_sorted = r(ind);
% remove duplicates before interpolation
[theta_unique,IA,IC] = unique(theta_sorted);
r_unique = r_sorted(IA);
% interpolation on n values to make it nicer
n = 360;  % 1 deg resolution
theta_n = linspace(min(theta_unique),max(theta_unique),n);
r_n = interp1(theta_unique,r_unique,theta_n);
% convert to cartesian
[xn,yn] = pol2cart(theta_n,r_n);
%% XY plot
figure(1),plot(x,y,'b.',xn,yn,'o');grid
%% polar plot 
figure(2),polarplot(theta_n, r_n,'--r')
Related Question