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I recently posted this question: Has this function been described/discussed?

It received two downvotes, and no explanation on why it isn't a good question. It received one answer, which got one upvote (by me, because even if it didn't actually answer what I was asking, it pointed me to aspects that I didn't realise could be at play) and one downvote. It also got several comments, most of which helpful (one of them actually came close to being an answer, pointing to the similarity between the function in question and Dirichlet's function - so it seems to be not completely unreasonable).

So I am asking, what makes the question deserving of downvotes, so that I don't commit the same mistakes in the future?

Or is this just a case of newbiephobia in the internet?

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    $\begingroup$ Just my two cents: I do not think it is an interesting question. You may consider any continuous, positive function over some interval and multiply it by the function that equals $1$ over rational numbers and $-1$ otherwise. Has this function been named before ? Probably not. Has this function some interesting property, besides being discontinuous? Probably not. $\endgroup$ – Jack D'Aurizio Oct 26 '17 at 17:54
  • $\begingroup$ Is a non-interesting question a bad question? $\endgroup$ – Luís Henrique Oct 26 '17 at 17:56
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    $\begingroup$ No, but it might attract downvotes for such reason. $\endgroup$ – Jack D'Aurizio Oct 26 '17 at 17:58
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    $\begingroup$ If this is about this one particular question, you should use (specific-question) tag. (If the question is used just as an example and you are actually after a more general question, then this tag should not be used. To me it was unclear which one is it, so I at least mentioned this in a comment, so that you can tag the question accordingly.) $\endgroup$ – Martin Sleziak Oct 26 '17 at 19:07
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    $\begingroup$ @LuísHenrique Unfortunately you cannot read the answer now. The answerer completely misread your question and thought that you are confused why $x^2 + y^2 =r^2$ cannot be written as a function. $\endgroup$ – user99914 Oct 26 '17 at 23:04
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    $\begingroup$ @LuísHenrique Since you bring it up, here is an image of the deleted answers. $\endgroup$ – Simply Beautiful Art Oct 26 '17 at 23:25
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    $\begingroup$ You received three purely mathematical comments by @5xum, quite appropriate and useful since they raised the exact problem with your question, namely, your misconceptions about the structure of the real line. Could you explain why you saw fit to leave the third one unanswered? (In fact you only came back two days later, to complain about the reception of your question, on main then on meta.) Neglecting mathematical comments which address the content of a question you asked is rude and at least as productive as invoking "newbiephobia" in this context, which is not much. $\endgroup$ – Did Oct 27 '17 at 11:27
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    $\begingroup$ @amWhy, thanks for your edit. I am reversing it, for two reasons - one, I do favour "realise" over "realize"; and two, I think asking about "newbiephobia" is an integral part of the question (indeed, I think it quite answers the question, since it became clear to me that the quesion wasn't a bad one, and that the downvoters didn't explain why they downvoted, because they had no reasonable explanation to offer). $\endgroup$ – Luís Henrique Oct 27 '17 at 13:24
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    $\begingroup$ To be honest, the use of the made-up term "newbiephobia," implying some fear-based bigotry of new users on part of the "elite" or something, is so insanely ignorant that I am not going to bother looking into the OP's question. While the sentiment and suspicion that people who are new here are unjustly discriminated against is nothing new, the implication that any such alleged discrimination must now have the suffix "phobia" attached to imply some out-and-out bigotry is ludicrous beyond belief. /1 $\endgroup$ – Ron Gordon Oct 27 '17 at 15:26
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    $\begingroup$ M.Se is like any large organization: all are welcome, but those who have built trust will be favored. Others who are just beginning here need to establish themselves first. That's what "rep" represents. It is not some form of mindless bigotry. It is the way the world works, or at least the way the world SHOULD work. But maybe I am just a dinosaur. /2x $\endgroup$ – Ron Gordon Oct 27 '17 at 15:29
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    $\begingroup$ "it became clear to me that the quesion wasn't a bad one, and that the downvoters didn't explain why they downvoted, because they had no reasonable explanation to offer" To give this summary of the various inputs above and below and on main is self-serving to the point of being dishonest. $\endgroup$ – Did Oct 27 '17 at 15:37
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    $\begingroup$ @LuísHenrique This is not, and never was about "newbiephobia". Using that "pointer" to put the blame on, instead of recognizing that you asked a poor question, and recognizing you are to blame for your question's reception, and not others, is sad. If any thing, you've been treated with "kid gloves", i.e. "newbie pandering", or call it "newbie pity". Stop whining, please. $\endgroup$ – Namaste Oct 27 '17 at 17:38
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    $\begingroup$ Louis You're passing blame along to users of this site, by attributing your downvotes to "newbiephobia", (blaming anyone who might have downvoted your question), a phenomenon you made up, in order to avoid taking the situation as a learning experience, if you were indeed wanting to learn. I understand that it is far more difficult for you to recognize that you asked a poor question and try to correct it, than it is to blame others for their feedback to you. Anyway, some users responded with pity on you, giving you pity upvotes, and patting you on the head. $\endgroup$ – Namaste Oct 27 '17 at 17:57
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    $\begingroup$ Also, your comment about pityful comments and pityful upvotes is an insult, not to me, but to the commentators and upvoters. $\endgroup$ – Luís Henrique Oct 27 '17 at 18:22
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    $\begingroup$ "It is quite obvious to me that the site has higher standards about questions than people are willing to admit." All SE sites, including M.SE, have high standards for questions (and answers, and general discourse). It is precisely those high standards that makes SE what it is. Regarding "admitting" that there are high standards, the standards are outlined in the help center, but maybe not 100% clear there. The clarity on standards is gained through experience. If you prefer to gain an understanding of the standards prior to asking, I suggest reading existing questions. $\endgroup$ – Todd Wilcox Oct 28 '17 at 20:44
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I think the first comment under your linked post points out a possible reason:

I have no idea what "it seems each of its points is rather an angle than a point;" means.

The mentioned sentence in your post is poorly written. As I understand, the "it" in "each of its points" refers to the function you give in your question. One would say "points of a set", or "points on the graph of a function", but not "points of a function". Moreover, saying a point "is rather an angle" does not make sense.

You responded in a comment as follows:

"it is discontinuous at every point, so that each point in the upper hemicircle is immediately followed by a point in the lower hemicircle - an an angle to the straight line between the point and its immediate predecessor."

Ok. It seems that you were really talking about "each point on the graph" of your function. But "each point in the upper hemicircle is immediately followed by a point in the lower hemicircle" is conceptually wrong: you are thinking that the rational and irrational numbers alternate on the real line. But NO: in the usual ordering of the reals no element has an immediate predecessor or successor. If you want know more about it, this is certainly not a bad question to ask on the main site.

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  • $\begingroup$ Yes, I meant "each point on the graph". I also get what you say about the alternation of rationals and irrationals. Thanks. Regarding angles, that's the way I learnt it; when a function is discontinuous, the corresponding point in the graph is an angle, and the function does not have a derivate at that point. Is that wrong? If so, well, its is wrong. I fear that if getting something wrong in a question will lead to it being downvoted, this site is not an adequate place to learn. I am not a mathematician or a an undergrad student in Maths. Do I have to be one to ask questions here? $\endgroup$ – Luís Henrique Oct 26 '17 at 21:35
  • $\begingroup$ No not at all. Just try to focus the next time on how you phrase your questions? $\endgroup$ – Anonymous196 Oct 26 '17 at 21:38
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    $\begingroup$ @LuísHenrique: "when a function is discontinuous, the corresponding point in the graph is an angle, and the function does not have a derivate at that point." I can guess what you mean though, this is not a precise way to describe what is really going on. There are different kinds of discontinuities. (cont) $\endgroup$ – Jack Oct 26 '17 at 23:33
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    $\begingroup$ @LuísHenrique: (cont)When a function is discontinuous at some point, it is not necessarily true that there is a cusp at that point on the graph of the function ("the corresponding point in the graph is an angle" is a rather cumbersome description and may be not understandable to native speakers of English). In fact, since your function is nowhere continuous (and nowhere differentiable), there can not be any "line segment" in the graph, and thus no "angle" would exist in the graph. $\endgroup$ – Jack Oct 26 '17 at 23:33
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    $\begingroup$ @LuísHenrique: "I fear that if getting something wrong in a question will lead to it being downvoted, this site is not an adequate place to learn." Well, knowing why and how something is wrong is part of learning, isn't it? Moreover, as it has been pointed out by others, phrasing a question in an accurate way is very important when asking/solving a problem: it not only helps others but more importantly yourself understand what you really need to ask/solve. $\endgroup$ – Jack Oct 26 '17 at 23:42
  • $\begingroup$ @LuísHenrique If you have a question you want to ask, then indeed "Do I have to be one to ask questions here?" is a resounding yes! We can only answer based on the quality of the questions asked. We cannot read minds, meaning we cannot glean "what you mean to ask, what you meant to ask, what you should have asked... what you didn't ask." And don't expect us to read your mind. We have nothing more to go on than the question you actually ask. Some people often ask for clarification, in case something is unclear, but bottom line: you want help: then make yourself as clear as possible. $\endgroup$ – Namaste Oct 26 '17 at 23:48
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    $\begingroup$ @amWhy, I think the OP meant "Do I have to be [a mathematician or an undergrad student in Maths] to ask questions here?" $\endgroup$ – Joel Reyes Noche Oct 27 '17 at 0:49
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    $\begingroup$ @JoelReyesNoche To that I will say most do not care. Besides, there's no way for us to be guaranteed you aren't lying about your credentials and background, hence I think we should judge all questions by fair standards. $\endgroup$ – Simply Beautiful Art Oct 27 '17 at 1:39
  • $\begingroup$ @amWhy We cannot read minds - indeed, and since we can't, it would be useful to point out why we are downvoting a question or an answer, particularly if it isn't downright obvious, wouldn't it? $\endgroup$ – Luís Henrique Oct 27 '17 at 12:48
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    $\begingroup$ @LuisHenrique: It may or may not be useful -- but it is certainly not something that should be required to accompany a downvote (nor an upvote). They serve site-necessary purposes that isn't "convince the person who wrote the post as to why it deserved a downvote". $\endgroup$ – Hurkyl Oct 27 '17 at 17:10
  • $\begingroup$ @Hurkyl - Yes, I understand that. But once I have asked a question, and am told that I shouldn't expected others to read my mind, I suppose it is only fair that I remind people that I am also not versed in the dark arts of mind reading? $\endgroup$ – Luís Henrique Oct 27 '17 at 17:35
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    $\begingroup$ @LuisHenrique: I'm not a mind reader either, so I don't know your intent for making the comment I replied to! My comment is a relevant response to the most common intent that people have when making such comments, and also to what readers might think after reading it. If it's not something that applies to what you actually mean, then don't take it as such. (and maybe even clarify the point of your comment, if so inclined!) $\endgroup$ – Hurkyl Oct 28 '17 at 4:36
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To make a more direct point, some users after reading your question would boil it down to something like:

Here's a function that I just made up. Has anyone seen it before?

In order for a question of this form to be a good question the construction of the function would need to have some motivation behind it, or there should be something "natural" about the construction. Contrary to that, anyone can just make up any old function, but it would be silly to ask if someone else had named or described that function before.

In your specific case, it's when you decide to break the square root into it's positive and negative branch based on whether or not $x$ is rational that you lose me. It seems like a completely unmotivated decision to pick the positive branch for rational $x$ and negative branch for irrational $x$. Why did you choose that? Why not rational vs irrational values of $r$? Why rational vs irrational values at all, and not some other partition of the reals?

I hope that this at least in part captures the attitude the downvoters had when they read your question.

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  • $\begingroup$ Well. This function occurred to me a few years ago, when studying calculus. It came from two considerations - discontinuity (having being introduced to the concept, I wondered, "can there be a function that is discontinuous for every value of x? - and the fact that the equation of a circle is not a function. Separating the equation into two different ones, with different domains, gave me a function that would be graphically represented by (something that looks like) a circle, and a function discontinuous for every value lf x. I showed it to the professor, and she commented it was... $\endgroup$ – Luís Henrique Oct 27 '17 at 18:59
  • $\begingroup$ ... "interesting", expressed some doubt whether it would be really discontinuous for every x ("I am not sure that the partition between rationals and irrationals is like that, can you prove me that there is always an irrational between two rationals, and conversely?") and told me she would "check it out" - but never actually returned to that conversation, nor did I. Sometime later, for different reasons, I realised that I was actually able to demonstrate its discontinuity for every x. And a lot of time later, I found stack exchange, and said to myself, "why not to ask this here"?... $\endgroup$ – Luís Henrique Oct 27 '17 at 19:05
  • $\begingroup$ ... which I am now convinced was a quite stupid decision to make. Will go elsewhere the next time I find something (that i (probably mistakenly) believe) puzzling about mathematics. $\endgroup$ – Luís Henrique Oct 27 '17 at 19:07
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    $\begingroup$ @LuísHenrique, it's a pretty good question to ask about the continuity of the function you made. It's silly to expect it to have a name. $\endgroup$ – Mike Pierce Oct 28 '17 at 20:21

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