varea.m

Compute the area and judge the direction of a closed curve.

Compute the area and judge the direction of a closed curve.
function area=varea(C)
%VAREA compute the "sign-area" of a closed curve.
% NOTE: Sign-area equals to the area of the closed curve when it is in anti-clockwise and equals to the negative area when it is in clockwise.
% Negative area means equal to area in magnitude but is negtive in sign.We can see that this script may also be used to judge the direction of a closed curve.
% C provides the coordinats of the nodes of the curve in the following way:
% C=[x1 x2 ...
% y1 y2 ...]
% AREA=VAREA(C)
% AREA returns the area of the curve(>0) when it is in anti-clockwise
% AREA returns the negtive area of the curve(<0) when it is in clockwise