polygeom.m

POLYGEOM computes area, centroid location, area moments of inertia and perimeter of closed polygons.

Description

POLYGEOM computes area, centroid location, area moments of inertia and perimeter of closed polygons.

This function is useful for bending/torsion stress analyses, area centroids of models for wind tunnel testing, rotational inertia for dynamics and blob analysis for image processing.

• MATLAB release: MATLAB 5.2 (R10)

[Elvis Dieguez]

Excellent program! Saved me lots of time trying to calculate the area surveyed by a moving wheeled sensor system.

[Finlay Scott]

Very useful for getting the perimeter of cyclic predator-prey ecological systems

[Thor I. Fossen]

Excellent program. Should be standard in Matlab. I have used it compute the centroids for wind and current projected areas as welll as other things:)

[Chinmay Pangarkar]

Super!!! I get all geometry of my arbitrary cells using this code. Thank you H.J. Sommer!!

[Alfonso Rojas]

Very useful program, clean and well-commented code. Tried it with Matlab
v 7.0.1 (R14), and it works fine. Excellent.

[Jim Price]

Yes, yes, yes --- this is an extremely useful and well-done script. Should be a part of the regular Matlab so that users can most easily find it. Thank You!!

[Pooya S]

Nice package

[Alice Huang]

 

[Xu]

Can't download ZIP instead of m file only?

[Xu]

 

[Stefan Berger]

This prog is wonderful, just what I needed. If you have time please improve it to handle the third dimension!!

[Raghuram]

The outputs are erroneous for the following input:
x = [1.0000 0.5000 0.8333 0.5694]
y = [1.0000 0.1667 0.5000 0.5694]
The centroid is computed as (0.8801,1.1496) which is outside the parallelogram formed by the input points.

[Richard Crozier]

Raghuram, the correct answer is given if you reorder your vertices so they are given clockwise around the outside of the polygon, rather than just specified randomly, e.g,

% Your vertices
% x = [1.0000 0.5000 0.8333 0.5694];
% y = [1.0000 0.1667 0.5000 0.5694] ;

% reordered moving clockwise around the polygon from (0.5, 0.1667)

xy = [0.5, 0.1667;
      0.8333, 0.5;
      1, 1;
      0.5694, 0.5694; ];
      
x = xy(:,1);
y = xy(:,2);

for i = 1:numel(x)-1
    line(x(i:i+1), y(i:i+1), [0,0], 'Color', 'b');
    hold on
end

line([x(end), x(1)], [y(end), y(1)], [0,0], 'Color', 'b');

[ geom, iner, cpmo ] = polygeom( x, y )

plot(geom(2), geom(3), '+r')

hold off

[Richard Crozier]

 

[Steve Tweddell]

Excellent function, a real time saver