# esda.shape.squareness

esda.shape.squareness(collection)

  Measures how different is a given shape from an equi-areal square

  The index is close to 0 for highly irregular shapes and to 1.3 for circular shapes. It equals 1 for squares.

  \[\begin{equation} \frac{ \sqrt{A}}{P^{2}} \times \frac{\left(4 \sqrt{\left.A\right)}^{2}\right.}{\sqrt{A}} = \frac{\left(4 \sqrt{A}\right)^{2}}{P{ }^{2}} = \left(\frac{4 \sqrt{A}}{P}\right)^{2} \end{equation}\]

  where \(A\) is the area and \(P\) is the perimeter.

  Notes

  Implementation follows [BC17].