Calculate the largest, smallest diameter and the centroid of a polyshape (irregula rpolygon) from a set of points

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Tesla
Tesla 2022-9-8
评论： Matt J 2022-9-9
I have a set of points (x,y) for a polyshape (almost 120 coordinates), I want to find the largest, smallest diameter and the centroid of this irregular polygon.

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Matt J
Matt J 2022-9-8
编辑：Matt J 2022-9-8
Ran in:
For the centroid, polyshape has a method centroid.
If the min and max feret diameters are what you want, then one approach would be,
pgon=nsidedpoly(4,'Radius',0.5); %input polyshape
fun=@(theta) feretDiam(pgon.Vertices,theta);
Theta=linspace(-pi,pi,1e4);
%Min Diameter
[~,i0]=min(fun(Theta));
[thetamin,minDiam]=fminsearch(@(t)fun(t),Theta(i0));
minDiam
minDiam = 0.7071
%Max Diameter
[~,i0]=max(fun(Theta));
[thetamax,maxDiam]=fminsearch(@(t)-fun(t),Theta(i0));
maxDiam=-maxDiam
maxDiam = 1.0000
function d=feretDiam(V,theta)
p=V*[cos(theta);sin(theta)];
d=max(p,[],1)-min(p,[],1);
end
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Tesla
Tesla 2022-9-9
Ran in:
Can you please tell me what the problem in this code:
pgon=nsidedpoly(4,'Radius',0.5); %input polyshape
fun=@(theta) feretDiam(pgon.Vertices,theta);
[~,xmin,ymin]=fun(thetamin);
Unrecognized function or variable 'thetamin'.
[~,xmax,ymax]=fun(thetamax);
plot(pgon);
line(xmin,ymin,'LineStyle','--');
line(xmax,ymax,'LineStyle','--');
function [d,xb,yb]=feretDiam(V,theta)
udir=[cos(theta);sin(theta)];
p=V*udir;
umax=max(p,[],1);
umin=min(p,[],1);
d=umax-umin;
if nargout>1
umax=udir.*umax;
umin=udir.*umin;
xb=[umin(1,:);umax(1,:)];
yb=[umin(2,:);umax(2,:)];
end
end
Matt J
Matt J 2022-9-9
Can you please tell me what the problem in this code:
The code doesn't include the lines that compute thetamin and thetamax.

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