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Let's say we have, on a 2d axis, four vertices that form a rectangle.

A rectangle is, from one perspective, a stretched out square... so you could say a rectangle is more 'skewed' than a square.

Is it possible to measure this 'skewness'?

I think of this in comparison to what I think are called 'regular' shapes, like a square, whose vertices are all the same distance from the average of the vertices. Aka any regular shape would have a 'skew' value of 0, and any non-regular shape would have a 'skew' value of more than zero.

I'm sorry if this doesn't make sense or if there is better terminology. I haven't studied mathematics beyond high school.

I have spent quite a number of hours trying to work on this myself, as well as a long while researching to see if I could find an answer. I did find maybe one or two pdf's about related subject matter, but I couldn't determine whether they answered my question or not as the maths was beyond me. I'm writing this from my phone so I don't have the links for the stuff I found.

EDIT I'm looking for an equation that can be applied to any number of vertices in random positions. The shape that these vertices form is not known. I've used the rectangle just as an easy example to explain my question.

The only information known is the coordinates of each vertex + any information that can be derived from that, such as the average vertex, the lengths of the edges between all pairs of vertices, etc etc

LangerNZ
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  • Letting the two sides of the rectangle be $a,b$ you can consider, for instance, $|a-b|$. Is this something along the lines of what you want? – Wojowu Aug 18 '19 at 11:47
  • I'm sorry I don't understand what $|a-b|$ means – LangerNZ Aug 18 '19 at 11:50
  • The absolute value of the difference between $a$ and $b$. Specifically, if $a\geq b$, then we just take the difference $a-b$. If $a<b$, then we swap them around and consider the difference $b-a$, so that the result is nonnegative. – Wojowu Aug 18 '19 at 11:50
  • I'm looking for something can be applied to any number of vertices in any number of positions.. so I don't know if finding the absolute difference would help. I'll edit my question. – LangerNZ Aug 18 '19 at 11:54
  • Ah, I see. I have taken the question as only asking about rectangles. Thank you for clarifying. – Wojowu Aug 18 '19 at 13:08
  • Are you talking about the angle at the vertices? Then you can compare to the interior angle of a regular n-gon. – Joel Pereira Aug 19 '19 at 00:57
  • That would be good I think, if I knew the shape that the vertices formed, but I don't know the shape they form, only their positions. – LangerNZ Aug 19 '19 at 01:05

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