What does Relevance mean exactly as a sort option for a search? What's the criteria behind it? It's an obscure unclear word. I did a search in the help center for it and got zero results back! Is it the number of times my keywords exist in the question? Across the answers as well? ...what?
I couldn't find much on the new Lucene-based search, and don't know much about the engine in general, so I'm asking this question.  Does anybody have a description of how search results are ranked?  Does the rank calculation include:   rep of post's author? views? unique referers? PageRank of referers? rank of questions that link to the post? whether a question is closed? vote count? answer count?
Galois Group of $\sqrt{2+\sqrt{2}}$ over $\mathbb{Q}$ How can I obfuscate (protect) JavaScript? Disabling middle mouse button Estimating Spline curve by OLS. Is a good idea to fix the knots at Chebyshev sites? I am writing my master's degree thesis on a novel method for fixing knots in an adaptive way and while reading the literature I've found many references to the so-called Chebyshev sites. This sites or points are basically the roots of the Chebyshev polynomials, and there's a proof showing that the Lebesgue constant (a measure that allows us to see how good is a polynomial interpolation) is very close to its lower bound if we put our knots in those sites. A practical guide to splines (De Boor, 1972) for example provides such a proof.  Anyway I am not interested in polynomial interpolation with splines, but in regression using LASSO on a set of B-splines . On Numerical methods in economics (Judd, 1998) it's stated that the results regarding the 'optimality' of the Chebyshev sites hold also for the regression case, but there is no proof showing that the latter is true.  I would like to know if it's a good idea to estimate the regression using B-splines constructed over a knot sequence given by the Chebyshev sites, since in the OLS framework I am not interested on minimising the Lebesgue constant but rather I want to minimise the $\| \cdot \|_2^2$. In many articles I've found phrases like "we will set the knots at the Chebyshev sites, that are well known to be good..." making allusion to the results presented in De Boor, but ignoring that those refer to the interpolation case.  If your could put some light on the problem I will be very grateful. Cannot get to a new line by hitting Enter I am using a Mac machine.  I asked a question, and then, someone answered it.    I clicked "Edit" to add a comment, and I would like to press Enter to go to a new line, but doing so submitted my comment and ended the edit instead. How to use grep and cut together? Lets say I'm doing a database for fruits. Using a text file for it, inside contains, in this format,  (Fruit:Quantity:Cost) Apple:10:1 Orange:20:2 Pears:10:3 Banana:20:4  10 Apples at $1 each. 20 Oranges at $2 each. 10 Pears at $3 each. 20 Bananas at $4 each.   My simple script goes like this:  echo "Enter fruit to find" read fruit  echo "Enter quantity to find" read count  echo "Enter cost to find" read cost  grep $fruit FruitDB.txt     It will display the fruits in the database.  But how do i use grep and cut together to find just by the quantity or the cost. In the quantity count area, let's say i enter 20, it will display the Oranges and Banana. Or when i enter count and cost, it will display just those that meet the conditions. (a) Solve the equation $yu_x+xu_y=0$  with the condition $u(0,y) = e^{-y^2}$. (b) In which region of the xy plane is the solution uniquely determined?     I did the first part but I don't understand how to do part b.  I read   But I don't understand how the argument is based. A more clear explanation is appreciated What is the significance of momentum? I just want to get an idea what  is. I know the mathematical meaning that momentum is $mv$ where $v$ is velocity. But I don't know its significance. Like I know that Acceleration is how velocity is changing with respect to time, I wanted to get feel of what momentum really is? Which package can be used to write BNF grammars? How to drive multiple LEDs from a Li-ion battery (with varying voltage)? How to fix "Notification access is not available" on Android Go? I've doing some researches since few days and I haven't really got an answer to my question.  I am in the process of building a huge file server for the company I work for. We bought a server case  with 24 bays and drives. Now I am stuck at the point where I have to choose the RAID card. I saw a RAID card from LSI that offer 6 internals mini-SAS 8087 ports (6x4) and would work perfectly with my build. However, it's not cheap.  I have been reading about the subject and I found something called SAS Expander. They are cheap.  with 6 mini SAS 8087 for 225$ (instead of 1150$ of the other one).  Now my question, how would I link an SAS Expander with a RAID card ? Do I need to a buy a RAID card with only 1 external 8088 port and link it with the other card ? Could someone clarify this for me because I haven't found any good documentation on it.  Thanks you. Self-promotion in chat We know from the  that it is accepted only in a limited way in answers and frowned upon if found to be spammy. We know from  that it can be deleted at any time from comments if the comment is not relevant or spammy.  But what about the chat? This leaves chat to be the only legitimate place to promote products or services that the user is affiliated to (albeit in an ad-like way).  What is your opinion? Can an abstract class have a constructor?  If so, how can it be used and for what purposes? How does reputation between the main site and its meta work on SE 2.0? I noticed that the reputation from the main site carried over to meta on Gaming (at least the first upvote), I guess that doesn't work the other way around, right?  Is it then impossible to have a meta reputation higher than the site reputation? How to use a flyback diode on a +/-12V motor I've got a motor hooked up to +12V on one side and -12V on the other, being driven in both directions by a Motor controller (). We were getting voltage spikes in the common ground after sending big impulses to the motor, so we put a flyback diode from the negative cable to the positive cable. However, this caused the motor to be less responsive in the reverse direction. How do we correctly prevent voltage spikes in the ground from this type of motor? Prove $(k,n+k)=1$ iff $(k,n)=1$ (a) Prove $(k,n+k)=1$ iff $(k,n)=1$. (b) Is it true that $(k,n+k)=d$ iff $(k,n)=d$? (all variables are integers, (a,b) means gcd(a,b))  For (a), I can only get so far.  $(k,n+k)=1\ \Rightarrow\ kq_1+(n+k)q_2=k(q_1+q_2)+nq_2=1$.  Note that we don't yet have that theorem (from a different class) that says something like if $d=(a,b)$, then $d$ is the smallest (or is it biggest) number which can be made by $ak_1+bk_2$, (which I'm not quite sure how it would help, anyway). So I'm stuck. Converting WKT to SHP? Every closed subset $E\subseteq \mathbb{R}^n$ is the zero point set of a smooth function In Walter Rudin's Principles of mathematical analysis Exercise 5.21, it is proved that for any closed subset $E\subseteq \mathbb{R}$, there exists a smooth function $f$ on $\mathbb{R}$ such that $E=\{x\in \mathbb{R}\mid f(x)=0\}$.   Since $E^c$ is open in $\mathbb{R}$, $E^c$ is a countable disjoint union of open intervals $(a_i,b_i)$. On an interval $(a,b)$, if we let $f(x)=\exp(\frac{1}{(x-a)(x-b)})$, $x\in(a,b)$; $f(x)=0$, $x\notin(a,b)$, ($f(x)=\exp(\frac{1}{(x-a)})$ or $f(x)=\exp(\frac{1}{(x-b)})$ on $(a,\infty)$ and $(-\infty,b)$ resp.), then $f$ is smooth. Hence we can get a smooth function on $\mathbb{R}$ such that $E$ is the zero point sets of $f$.  (1). How about a closed subset $E$ of $\mathbb{R}^n$? is it true that for any closed subset $E\subseteq \mathbb{R}^n$, there exists a smooth function $f$ on $\mathbb{R}^n$ such that $E=\{x\in \mathbb{R}^n\mid f(x)=0\}$?  An open set in $\mathbb{R}^n$ cannot be written as a disjoint union of countable open balls hence the proof above is not valid. The partition of unity only claims that for an  open set $U$, there exists open $V$ in $U$ such that $\bar V\subseteq U$ and a smooth function $f$ on $\mathbb{R}^n$ such that $supp f\subseteq U$, $f|_V=1$.   (2). The taylor series of $f(x)=\exp(\frac{1}{(x-a)(x-b)})$ does not converge around points $a,b$ hence $f$ is not analytic at $a,b$. Is it true that for any closed subset $E\subseteq \mathbb{R}$, there exists an analytic function $f$ on $\mathbb{R}$ such that $E=\{x\in \mathbb{R}\mid f(x)=0\}$? Can I recover a file from /dev/null?