How to calculate Area of polygon by Simpson's rule using coordinates?

Question

This code uses Simpson's rule , but gives the wrong area of a polygon by the formula:

def defineArea(xCoords, yCoords):    

    i = 0
    sum = 0
    for i in xrange(len(xCoords) - 1):         
        result = (xCoords[i] - xCoords[i+1])*(yCoords[i]+ yCoords[i+1])

        i +=1
        sum = 0.5*(sum + result)
    print "Total 2D area is: ", sum*

What I am doing wrong? How do I calculate the area of polygon by Simpson's rule using only coordinates?

Answer 1

Don't do sum = 0.5*(sum + result) inside the loop. Also, you don't need the sum variable at all once it's outside the loop. Just do result = 0.5 * result after the loop is complete, then print result .

You also need to switch the order of xCoords[i] and xCoords[i+1] .

Answer 2

Do what "Bill the Lizard" said (sorry I can't post a comment yet), or you can do it inside the loop too:

sum = sum + 0.5*result

Also, you are doing (xCoords[i] - xCoords[i+1]) instead of (xCoords[i+1] - xCoords[i])