# PrA

Revision as of 15:35, 12 May 2022 by KevinYager (talk | contribs) (Created page with "'''PrA''' is a simple ad-hoc parameter to define the "non-circularity" or [https://en.wikipedia.org/wiki/Ellipse eccentricity] of a 2D object. This quantity is simply: :<math>...")

**PrA** is a simple ad-hoc parameter to define the "non-circularity" or eccentricity of a 2D object. This quantity is simply:

Where is the object's perimeter, is its surface area, and is an effective size (radius), computed based on the corresponding circle of the same area:

This definition of PrA is convenient, since it provides a simple measure of eccentricity. In particular, for a circle one expects:

Since a circle has the minimal perimeter (for a given area), this is a limiting value of PrA:

And thus any non-circular object will have a larger PrA.