Finding segmented triangle area of polygon

I tried to find out the triangle area in the polygon based on determinant theory.

Here is the reference

I tried to calculate the area of triangles using indeces: function and for-loop.

function area = trianglearea(a)


for i = 2 : length(i)-1;
    tri = [a(1,1), a(1,i), a(1,i+1); a(2,1), a(2,i), a(2,i+1); 1, 1, 1];
    area = 0.5*det(tri)
end
end

A = [0 10 12 8 6 0; 0 1 4 6 8 0];
trianglearea(A)

then the results is

and workplace is the results of area of triangles do not show each reasults following different i value in for-loop. It just show the final result when i = lengh(a)-1.

How can I display every triangle area..?

Answer 1

[Chidvi Modala]

You can make use of the following code to capture the area of each triangle and also to find the area of entire polygon

function [area, totalArea] = trianglearea(a)
area = zeros(length(a)-2,1);
for i = 1 : length(area)
    tri = [a(1,1), a(1,i+1), a(1,i+2); a(2,1), a(2,i+1), a(2,i+2); 1, 1, 1];
    area(i) = 0.5*det(tri);
end
totalArea = sum(area); % Total Area of polygon
end

[SeungHyun Cha]

Thank you

Answer 2

[Image Analyst]

Or simply use polyarea().

[SeungHyun Cha]

Thank you