Assigning incrementing id for each feature group in attributes with QGIS expressions
Increment value based on grouped field
Looking for an intuitive explanation why the row rank is equal to the column rank for a matrix I am looking for an intuitive explanation as to why/how row rank of a matrix = column rank. I've read the proof at  and I understand the proof, but I don't "get it". Can someone help me out with this ?   I find it hard to wrap my head around the idea of how the column space and the row space is related at a fundamental level. Why are most of the main characters White/English in Game Of Thrones? Okay, I was thinking about the series of Game of Thrones and all the battles and stuff, and I thought why aren't there any characters beside White/English characters that have main/important roles? Can you name any that are alive that are anything else beside White/English?   This is a short list of some of the main characters (all White/English):   Cersei - Queen and important political Lannister. Jaime - Guy who is father to the late king and is King slayer. Tyrion - Short guy in politics who is currently on the run(that's what the wikia told me). Daenerys - Queen who is freeing people and dragon owner.   And the list goes on and on, why aren't there any characters other than Caucasian characters that are in the series?  I've read a lot of articles on the internet about this after Googling around, and none of the articles I read had any scientific evidence or research - it was just conjecture.  So, are there any actors/characters from racially diverse backgrounds? I'm hoping for canon evidence (pictures, links, quotes) from the book and/or TV show. In the case of actors, can you also list their role?    This is not intended as a racist question. I just want to know why, since the story takes place over a large area, there doesn't seem to be any diversity. Nested List Indices Reference help for "fuzzy mathematics" I want to study Fuzzy Sets and Fuzzy logic self. For that what would be better book to start from basic? Cannot change brightness setting using function buttons or using the brightness control bar on HP laptop Please make the multiple comment timer less annoying (non-resetting etc.) As a little feature to prevent comment spam, you can only enter one comment every 15 seconds. That's a very reasonable limitation, since you very rarely have a good reason to write comments that quickly. I've only seen it twice at all, I think, but both times it was extremely annoying.     Only 1 comment allowed per 15 seconds; timer reset.   The reason is that every time you hit the limit, the 15 seconds begin anew. You have no indicator that tells you when you are allowed to comment again, and if you hit enter after just 14 seconds, you're back to zero. Yesterday, I went through four cycles of not quite 15 seconds, counting in my head, before I got a myself a coffee and tried again afterwards.  I suggest that you do one or more of the following (in decreasing order):   Make the counter non-restarting Add a visible countdown Make it clearly visible that you can't comment right now You can actually increase the waiting time, if it is clearly visible and there is no unnerving invisible countdown. Actually, just remove all comment fields after one comment, and tell the user to reload the page. Just please don't have UI elements that look like they would work, but feel like they are trolling you. I'm using Rules 7.x-2.6 and the way it works has changed a bit since I last saw.  I have a rule as follows:  EVENT A node has been flagged, under "Report content"  CONDITIONS None  ACTIONS Send mail to [site:mail]   However, I'd like to, instead of sending directly to [site:mail], send an email to all users flagged with an "admin" role.   Now I know that I'll need to provide a loop do so, but my sticking point is generating the list of users to pass to the loop. So far, I have attempted to add a new action:   "Fetch entity by property" Entity type: User Property: User roles Value: admin   But this doesn't seem to give me what I want in data selection, when passing it to the loop. Can someone recommend what they would set here? When I tried to connect my Ubuntu 13.10 to my VM Centos 6.5 using ssh appear the message "Connection refused" or "No route to host" even than I change the port, noting change.    I need to use SSH, VPN and Samba, but this IP in my VM Centos do not work.  How Can I resolve this problem? Show that quotient rings are not isomorphic I've been given a homework problem that requires me to show that the rings $\mathbb{C}[x,y]/(y - x^2)$ and $\mathbb{C}[x,y]/(xy-1)$ are not isomorphic.    This is my attempt at a solution:  For $\mathbb{C}[x,y]/(y - x^2)$, we can parametrize in the following way: $x = t$ and $y = t^2$. Then this ring is isomorphic to $\mathbb{C}[t]$.  For $\mathbb{C}[x,y]/(xy-1)$, we can parametrize $x = t$ and $ y = 1/t$. Then this is isomorphic to $\mathbb{C}[t, 1/t]$.   But $\mathbb{C}[t, 1/t]$ is not isomorphic to $\mathbb{C}[t]$.  Am I on the right track? If not, any helpful hints? Odds made simple Finding where source has branched from git Hey guys I am currently working on a scene with multiple objects.  There is one object (a wheel) that I need to rotate the origin for without rotating the wheel itself.  I have the exact angle that I need so a manual solution would be the best.  Any help would be much appreciated. I am used to parametric modeling and Blender is a little out of my depth. A strict equality operator will tell you if two object types are equal. However, is there a way to tell if two objects are equal, much like the hash code value in Java?  Stack Overflow question  is similar to this question, but requires a more academic answer. The scenario above demonstrates why it would be necessary to have one, and I'm wondering if there is any equivalent solution. gnome-terminal instantly closes after messing with the profile settings I am using Gnome Terminal in Ubuntu 14.04 and I modified the profile preferences, setting it to start with a custom command instead of the default. I can't remember what that custom command was, but now when I launch the terminal, it instantly closes.   Is there any way to change the profile preferences in terminal without having it open? How to ask a smart question The title of  of  is, "Is it posible [sic]?"  This doesn't provide any information at all. It should be mandatory for everyone asking questions on the Internet to read , which says:     Help your community learn from the question. When you field a good question, ask yourself "How would the relevant documentation or FAQ have to change so that nobody has to answer this again?" Why does WCF return myObject[] instead of List like I was expecting? Lisp Executable I've just started learning Lisp and I can't figure out how to compile and link lisp code to an executable.  I'm using clisp and clisp -c produces two files:   .fas .lib   What do I do next to get an executable? Can a shell script set environment variables of the calling shell? Let $\mathbb F$ be a field and $\mathbb  K $ be an extension field of $\mathbb F$  such that $\mathbb K$ is algebraically closed.   Let $\mathbb L$ be the field of all elements of $\mathbb K$ which are algebraic over $\mathbb F$. Then $\mathbb L_{|\mathbb F}$ is an algebraic extension.   My question is : Is $\mathbb L$ algebraically closed ?  I am trying to prove the existence of algebraic closure, so please don't assume that every field has an algebraic closure. I have a basic doubt about the associativity of the cartesian product. Well, first wikipedia says that the cartesian product isn't associative, and there's a good argument for it: if $x\in E$, $y\in F$ and $z \in G$ the identity $((x,y), z)=(x,(y,z))$ would imply that $(x,y) =x$ and $(y,z) = z$ so that $((x,y),z)=(x,y,z)$ would mean nothing.  That's fine, I like this argument. However, in his book Calculus on Manifolds, Spivak says that the cartesian product is associative. He says: if $A \subset \mathbb{R}^m$, $B\subset \mathbb{R}^n$ and $C \subset \mathbb{R}^p$ then $(A\times B)\times C = A \times (B \times C)$, and both of these are denoted simply by $A \times B \times C$.  Well, this confuses me because Spivak is always very rigorous, so that he wouldn't state something that's not true in such way. Is Spivak or Wikipedia right ? Or Spivak's statement only works for subsets of euclidean spaces ?  Thanks in advance and sorry if this question is too basic.