Distance from a point to polygon

Distance from a point to 2-D polygon

Description

%*******************************************************************************
% function: p_poly_dist
% Description: distance from pont to polygon whose vertices are specified by the
% vectors xv and yv
% Input:
% x - point's x coordinate
% y - point's y coordinate
% xv - vector of polygon vertices x coordinates
% yv - vector of polygon vertices x coordinates
% Output:
% d - distance from point to polygon (defined as a minimal distance from
% point to any of polygon's ribs, positive if the point is outside the
% polygon and negative otherwise)

• Acknowledgements: This submission has inspired the following:; Distance from a point to polygon
• MATLAB release: MATLAB 6.0 (R12)

[Kardi Teknomo]

 

[Jesse Collins]

this function would benefit greatly from also returning the point on the given polygon closest to the point from which the distance is to be found.

[Eric Schmitz]

For the case where a polygon rib is either horizontal or vertical, the test for checking if the projected point is inside a segment may not work all the time because of numerical accuracy. I added a test to force either the x or y coordinate of projected point to be set equal to the corresponding rib x or y coordinate (before the section computing idx_x and idx_y):

id = find(diff(xv)==0);
xp(id)=xv(id);
clear id
id = find(diff(yv)==0);
yp(id)=yv(id);

[Alejandro Weinstein]

I added the suggested test from Eric Schmitz, and also return the point of the polygon closest to the point. It is available here:
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=19398&objectType=file

[Cristian D]

Thanks for this function! it was very usefull!

[Xavier Nieves]

Hi, I have been trying to create a function similar to this one... if I were to have a random polygon but always have as an input the x,y coordinates of the vertices's and and the x,y coordinate of a point. can I use this function to determine the minimum distance of the point to the polygon, and if I can should express the inputs in what way... ?? nice function