Display credit in map composer? I am trying to publish maps from QGIS Map Composer.  I would like to automatically add the credits of the background layers displayed in the composition (like OSM, Bing, ...)  I am aware of such a feature in main QGIS window using  View -&gt; Decorations -&gt; Copyright label but    this data is not shown in composer I am looking for an expression to adapt the text depending of the active layer    (Currently using either qgis 2.18 or 3.4)
Showing OSM source acknowledgment on the map in QGIS? I am using OpenStreetMap as a base layer via XYZ tiles in QGIS 3.01.  I can't seem to find a way of having source acknowledgement appear on the lower right corner of the map.  Can somebody point me in the right direction?
Remove duplicate rows in MySQL Let $x = (a, b), y = (c, d) \in \mathbb{Z}^2$. What is the condition on $a, b, c, d$ so that ${x, y}$ is a basis?   My answer: $ad\neq bc$ and $gcd(a, c) = gcd(b, d) = 1$.  The first condition ensures that they aren't the same vector; the second ensures that we can actually "get" all of the integer values/lattice points.  Is this correct?  Thanks. Following the guidelines suggested in , I am going to post a proposed proof as an answer to the theorem below. I believe the proof works, but would appreciate any needed corrections.  Theorem If a series $\sum_{n=1}^{\infty}a_n$ of real numbers converges then $\lim_{n \to \infty}a_n = 0$ Consider the subset $B=\{(x,y):x^2+y^2\leq 1\}\ \subseteq \mathbb{R}^2$. Show that $\vert B \vert = \vert \mathbb{R}^2 \vert$.  It is easy to see tht $f:B\rightarrow\mathbb{R}^2$ defined as $f(x,y)=(x,y)$ is injective.   However, in the book I'm working out of (Book of Proof by Richard Hammack), the other injection noted is  $g:\mathbb{R}^2\rightarrow B$ defined as  $$g(x,y)=\left(\frac{x^2+y^2}{x^2+y^2+1}x,\frac{x^2+y^2}{x^2+y^2+1}y\right).$$  In the book I'm asked to verify this is indeed an injective function.  My approach was to assume $g(x,y)=g(m,n)$ and through basic algebra I was able to deduce  $x(m^2+n^2+1)(x^2+y^2)=m(x^2+y^2+1)(m^2+n^2)$  and  $y(m^2+n^2+1)(x^2+y^2)=n(x^2+y^2+1)(m^2+n^2)$  but how does this show $(x,y)=(m,n)$? Or is this the wrong approach? I'm having a difficulty in finding one way car rentals from Alaska, which I can return in Seattle.  Do all the main rental agencies restrict such one-way rentals, as they involve crossing through Canada, before entering the lower 48 states? Why did my electric range wiring burn out at the terminal block? Turned on our 2 year old stove (Whirlpool Gold) and heard fizzing noises, then smelled electrical burning. Went downstairs and shut off the breaker (40 amp). That was the only way to get it to stop "fizzing". (6 gauge wire by the way). The range is 240 volt electric 3 wire hooked up to a 40 amp breaker (6 gauge wire). When I took the back panel off the stove I saw exactly where the problem occurred. The black wire was burned, the terminal block was melted, and the inside of the back metal panel that I removed was pitch black in the spot that was facing that area before removal. I removed the stove top and inspected all wires and other electronic components. No problems at all.   So my questions are:    Why did the black wire only, at the terminator block, start burning?  Why did the breaker not pop off?  Is it safe to just replace the terminator block or is this an indicator of a much larger problem?  Is 6 gauge the correct gauge for a 40 amp breaker? Why does SQL Server use a better execution plan when I inline the variable? I have passed the calc sequence, and thought that I understood things.  But I have trouble with limits now and again.  From the way I understand it, the 'best' way to evaluate a limit, is to evaluate the expression at the number in the limit.  In that way it's not only a limit, but an algebraic expression (so, I think, the need for limits goes away entirely, superseded by accuracy.)  But then I see something like $\lim_{x\to 2} \frac{x^2-4}{x-2}$.  Now, I think in my mind 'the best way to evaluate this is just to plug in $2$'  But it doesn't work that way, as the limit is $4$, and if I plug in, the answer is $0/0$.  I think that people here, with their natural talent in math, can perceive where my train of thought is going wrong, and correct me.  Please! How to combine measurement error with statistic error We have to measure a period of an oscillation. We are to take the time it takes for 50 oscillations multiple times.  I know that I will have a $\Delta t = 0.1 \, \mathrm s$ because of my reaction time. If I now measure, say 40, 41 and 39 seconds in three runs, I will also have standard deviation of 1.  What is the total error then? Do I add them up, like so?  $$\sqrt{1^2 + 0.1^2}$$  Or is it just the 1 and I discard the (systematic?) error of my reaction time?  I wonder if I measure a huge number of times, the standard deviation should become tiny compared to my reaction time. Is the lower bound 0 or is it my reaction time with 0.1? Sci Fi action movie where an elite group of people control business through a game they play online I saw a movie where people are running from a group of powerful killers or a naughty company/organization.  A woman was hired to find the entity/company. A very overweight Asian man talks to them on line at one point. (When I say overweight, I mean 400 pounds plus)  He talks to a virtual dolphin and tells it he is sorry but he cannot play with the dolphin that day. Eventually, the people find the fat guy in real life. He is sitting on a Chinese style boat in a river (I think it was a river). (He is sitting in the rear of the boat. The boat is rather small. He is wearing a loin wrap like a sumo wrestler. In fact, I should most likely call him a sumo wrestler to describe the look.)  He had implants and wires coming out of his head like the Borg Queen did.  There is another part in the movie, where he replies to someones concern, saying, "I live a life of wonder..." (or something similar).  By the time the movie is over, the evil force has caused his death. A team of Yakuza style (might actually be the Yakuza) commandos tear through everything trying to stop the truth from being discovered. The huge Asian man ends up leaving little messages, like parts of himself, to guide the woman to the truth. The ending reveals the naughty company/organization is a group of elite power brokers that control business by playing a game. Corporations lose or gain ground over nothing more than the turn of a game. (Including totally going out of business or making a fortune from nothing.)  Do you have any idea what movie this was? Is there a way to disable a specific JS script from a specific website? I want to disable a specific JS script from a specific website without disabling the javascript completely. Is there a way to do that ? Packed images used as background don't show up when reopening the file I have seen a single (1) mention of View port background images disappearing when the .blend file is saved and reopened.  However...the answers are not relative to what I am experiencing.  I go through the trouble of setting up four images (top, side, front, back) and then pack these images using External Data &gt; Pack all into .blend and then I save the .blend.  I save the file, open it back up, and the background images are all gone. Open up properties panel, look to see background images check box is unchecked, click add image, and choosing the open drop-down arrow...the data paths still show the list of images (packed into a specific folder textures).  They are still there, the data set is intact.  Why is It that I have to set this up each and every time I open the file.  It seems like earlier versions &lt;2.76B saved the images and saved the file with the background images check box checked without the need to set this up each time the file is reopened.  This is getting very frustrating due to the fact that a few of the background images mus be set up using Blender's rotate, scale and move tools to align the background image up with the model I have already fabricated.  Thanks! I have this, in D1:  =sum(D3:D)   I want D1 to always be the sum of the rest of column D (D2 is a header)  I sometimes move a row, from eg 8 to 3, and that causes D1 to change to sum(d4:d).    I want D1 to stay as my sum of the column. show that if $a | c$ and $b | c$, then $ab | c$ when $a$ is coprime to $b$. Given two numbers $a$ and $b$, where $a$ is co-prime to $b$,     Show that for any number $c$, if $a|c$ and $b | c$ then $ab| c$. Is the reverse also true? In other words, if $ab |c$ and $a$ is co-prime to $b$, then do we have $a | c$ as well as $b|c$? Is an apostrophe with a decade (e.g. 1920’s) generally considered “incorrect”? I typically don’t use an apostrophe with plurals in any situation, but I always assumed that the use of an apostrophe in constructions like acronyms:     Forty BA’s were given out to students this year.   or numbers:     Though the greatest period instability occurred during the 1950’s when. . . .   was more or less ok. I would personally use BAs and 1950s here, but I've never thought the apostrophe in this case was necessarily “incorrect”. What say ye? How would I implement a binary search using just an array? How can aperture be f/11 on a lens with an aperture range designation of 3.5-5.6? What does the "yield" keyword do? What is the use of the yield keyword in Python? What does it do? For example, I'm trying to understand this code1: def _get_child_candidates(self, distance, min_dist, max_dist):     if self._leftchild and distance - max_dist &lt; self._median:         yield self._leftchild     if self._rightchild and distance + max_dist &gt;= self._median:         yield self._rightchild    And this is the caller: result, candidates = [], [self] while candidates:     node = candidates.pop()     distance = node._get_dist(obj)     if distance &lt;= max_dist and distance &gt;= min_dist:         result.extend(node._values)     candidates.extend(node._get_child_candidates(distance, min_dist, max_dist)) return result  What happens when the method _get_child_candidates is called? Is a list returned? A single element? Is it called again? When will subsequent calls stop?   1. This piece of code was written by Jochen Schulz (jrschulz), who made a great Python library for metric spaces. This is the link to the complete source: [Module mspace][1]. Why do Americans have to file taxes, even if their only source of income is from a regular job? Ackermann function - how to calculate the number of times it calls itself Purely for my own amusement I've been playing around with the .  The Ackermann function is a non primitive recursive function defined on non-negative integers by:  $A(m,n) = n+1$, if $m=0$  $A(m,n) = A(m-1,1)$, if $m&gt;0$ and $n=0$  $A(m,n) = A(m-1,A(m,n-1))$, if $m&gt;0$ and $n&gt;0$  I'm not interested in values of the function itself, rather I'm interested in the number of recursions the function takes to arrive at a value. For example:  $A(1,2) = A(0,A(1,1)) = A(0,A(0,A(1,0))) = A(0,A(0,A(0,1))) = A(0,A(0,2)) = A(0,3) = 4$  That's 6 steps, so if we define $RA(m,n)$ as the number of recursions to calculate $A(m,n)$, then $RA(1,2) = 6$.  I made a short Excel macro to calculate $RA(m,n)$ for any given $m$ and $n$. The problem I have is that $RA(m,n)$ grows even faster than $A(m,n)$ and I quickly run out of stackspace. The table below shows $RA(m,n)$ for very small values of $m$ and $n$. The numbers shown for $RA(3,10)$ and $RA(4,1)$ are the number of steps before crashing!    A formula for $RA(1,n)$ is trivial, and it is relatively easy to see that $RA(2,n) = 5(n+1) + 4n(n+1)/2$.  So my questions: can anyone see an explicit formula for $RA(3,n)$? More generally, does a formula exist for $RA(m,n)$, in the same way that $A(m,n)$ can be expressed using Knuth arrows?   For the low values shown of $m$ and $n$, $RA(m,n)$ looks about order of magnitude larger than $A(m,n)$. Can we prove that $RA(m,n) &gt; A(m,n)$ for all $m,n$. Intuitively, it should be.  For bonus points, can $RA(m,n)$ be expressed in terms of $A(m,n)$?