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 Apr 10 comment Is there a name for the curve $\sqrt{x} + \sqrt{y} = k$ @RecklessReckoner yeah, the blue part is common to this and "star shaped" thing with four points. Apr 10 accepted Is there a name for the curve $\sqrt{x} + \sqrt{y} = k$ Apr 10 comment Is there a name for the curve $\sqrt{x} + \sqrt{y} = k$ The a hyperbola $xy=k$ is called a rectangular hyperbola, as, I assume, it's contained by the coordinate axes, rather than the diagonals. I wonder if (un-)rectangular parabola is a suitable name here. Apr 9 comment Is there a name for the curve $\sqrt{x} + \sqrt{y} = k$ @RecklessReckoner It looks pretty much identical to the parabola $(1+x^2)/2$ rotated about the origin by 45 degrees. Apr 9 asked Is there a name for the curve $\sqrt{x} + \sqrt{y} = k$ Feb 14 awarded Popular Question Oct 6 awarded Yearling Oct 6 awarded Yearling Jul 2 awarded Curious May 15 comment Axis of symmetry of a binary image I understand that. It seems like a sensible optimisation when there is a single convex shape (and some cases which are not). I was more trying say that even if you skipped the efficiencies it would be faster. I just read what I wrote in the message above, I don't know why I said "compatible to", I definitely meant to say "faster than". That said, the down-/sub- sampling method has the advantage of "softening" the optimisation landscape, and will perform better in some cases - but it really depends on the images, and what kind of result is needed. May 15 comment Axis of symmetry of a binary image I would expect, even if you didn't use the binary search, and just brute-forced every possibility, it would still be comparable to a particle based search. i.e. (1000 particles)x(1000 iterations) is probably larger than (180deg at 3deg itervals = 60angles)x(image diagonal in pixels). May 15 comment Axis of symmetry of a binary image Indeed, but it's a vanishingly unlikely case. (technically you're not going to do any better than $C_4$ symmetry in an image. - assuming > 1 pixel is different) May 15 comment Axis of symmetry of a binary image @String a line of symmetry that passes through the centre of mass would probably be a good starting point for an algorithm. May 15 revised Axis of symmetry of a binary image added 95 characters in body May 15 answered Axis of symmetry of a binary image May 15 comment Axis of symmetry of a binary image OK, I'll outline what I mean in an answer. May 15 comment Axis of symmetry of a binary image I'd say do it as an optimisation. But you could optimise your optimisation proceedure by doing things like taking a initial approximations using a low resolution image, or by sparsely representing the image in terms of edges, or a randomly sampled subset of your image. It'll still be a bit slow. There's loads of algorithms for these things if you look at the machine vision literature, but if you want something quick and dirty that works, a few optimisations on a brute force search would be the way forward IMO May 15 comment Find the minimal value of a function May 3 comment Matlab iteration @user142176 The answer is always zero. So function j=iter(p,q,m,e); return 0; end. Also, your code would work if line 3 was j=0, but I think there might be a mistake somewhere in the specification of your problem. May 3 answered Matlab iteration