Compute area of polygon

gistfile1.txt

Source: https://www.johndcook.com/blog/2018/09/26/polygon-area/

Shoelace formula:
x1 y2 + x2 y3 + … xn y1 – y1 x2 – y2 x3 – … –  yn x1

Python implementation
def area(x, y):
        n = len(x)
        s = 0.0
        for i in range(-1, n-1):
            s += x[i]*y[i+1] - y[i]*x[i+1]
        return 0.5*s