Polyarea function concave or convex

I want to know whether the built in function polyarea finds the area of data points bounded by concavehull or not. If it is bounded by convex hull, It would really affect the accuracy of my result.

Answer 1

[John D'Errico]

polyarea allows completely general polygons. It does NOT give you the convex hull area. (This is 100% certain.) But, since nobody should ever believe the line "just trust me", trust MATLAB instead:

Here is a polygon with known zero area, because it traces around 3 vertices, but then retraces its path. The area of the convex hull would be 1/2.

py = [0 1 1 1 0];
px = [0 0 1 0 0];
polyarea(px,py)
ans =
     0

Yet polyarea gives the correct answer of zero.

Answer 2

[Matt J]

An easy way to check is to compare with convhulln. Convhulln definitely computes the area of the convex hull. I don't see why polyarea would exist if it is redundant with convhulln.