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bio website whereofonecannotspeak.wordpre…
location Brighton, United Kingdom
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visits member for 2 years, 11 months
seen Sep 7 at 16:50

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
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
Hint: en.wikipedia.org/wiki/W_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
1
comment Whats the intergral of xe^-y dy dx with 0 and 1 as limits
Often a second symbol is omitted, though it is a bit ambiguous in this case. I'd read it with [0,1] for both integrals. But reading it as an indefinite integral over x might be valid too.
Apr
24
comment Does relative positive definiteness have a good name?
@PavelJiranek This little exchange has helped me figure out what I need to write. Thanks :)
Apr
24
comment Does relative positive definiteness have a good name?
@PavelJiranek Indeed. The thing I'm trying to articulate in the thing I'm writing is just a sense of "bigger", that's about all that matters for my purposes. This kind of technicality (and quarrel) poses a real danger of distracting the reader from what should be a really simple and intuitive point, as well as confusing and alienating them.
Apr
24
comment Does relative positive definiteness have a good name?
@PavelJiranek Oops, I'll edit it. The point of avoiding it is that most people will be unfamiliar with the idea of partial orderings. I'm already asking my audience to grapple with a number of unfamiliar topics. I don't want to make it worse if I can help it.
Apr
24
comment Does relative positive definiteness have a good name?
That's an excellent suggestion.
Jul
5
comment Difference of two exponential RVs
insularity of [my] analysis", perhaps just say that, instead of pretending that you actually care about what I have to say. It would save us both a lot of time.
Jul
5
comment Difference of two exponential RVs
Yes - we did not reach the said conclusions, you did, passing your own judgement off like we'd actually discussed it, agreed, and come to some mutual agreement is rude. You were pretty adamant that you didn't follow what I was saying, so I do not see how that could be the case, unless you were only feigning ignorance, which would be both rude and annoying. Yes, there are plenty of mathematicians who like the notion that mathematical truth is detached from reality, not saying your one of them, but they most definitely exist. Now, if you do indeed wish to "[draw] my attention to the ...
Jul
5
comment Difference of two exponential RVs
Not really, that would most likely be choosing your description so that the maths is easy, not for the type of simplicity described by the pragmatic maxim. // we is the incorrect personal pronoun here (and typically rude) - the advantage is realism, whilst I understand that doesn't matter for many mathematicians, it does to others. Just because I think using $1_x$ is stupid, does not mean that I do not know why others choose to use it, in fact I use it myself sometimes, but I still consider it to be a hack. Likewise, writing a computer algebra system that way would end in disaster.
Jul
4
comment What does δA mean in differentiation?
That's by Leonard Susskind right, from his online lectures I thought he was quite a good teacher - are you using those too?
Jul
4
comment Generalised logaritmic function
Cool, seems the problem is much deeper than I thought when I wrote the question.
Jul
3
comment “universe” in set theory and category theory
Just thought I should add that the "universe of discourse" is used more widely than mathematics, usually referring to a group of people sharing similar assumptions discussing the similar things (though not usually a set)
Jul
3
comment Comparing uniform priors
I am. I have seen this problem a number of times, have explained it below...