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Jan 14, 2017 at 3:57 vote accept j.s.
Jan 14, 2017 at 3:57 comment added j.s. @Ben Barber: Thank you so much for this wonderful answer.
Jan 13, 2017 at 23:06 comment added Ben Barber Given a permutation, we can draw its graph (in the sense that functions have graphs) as a subset of $\mathbb R^2$. Then inversions correspond precisely to pairs of points joined by a line of negative slope. Note that the actual $x$ and $y$ coordinates aren't important: all that matters is their relative order. This is only obvious if you've seen it before!
Jan 13, 2017 at 22:31 comment added j.s. @Ben Barber: A Genius Answer. thanks. But It's not perfectly clear to me why the class of permutation graphs are equivalent to graphs constructed by assigning a point in plane to each vertex and connecting two vertices by an edge when the line joining them has negative slope. Is this obvious?
Jan 13, 2017 at 13:47 comment added T. Amdeberhan Quite interesting.
Jan 13, 2017 at 13:34 history answered Ben Barber CC BY-SA 3.0