How to get number of "columns" in an Array in Array?
How to efficiently count the number of keys/properties of an object in JavaScript?
Norman Window Optimization Suppose $G=\{a_1,...,a_n\}$ is a finite abelian group, and let $x=a_1a_2\dotsm a_n$.   Prove that if there is more than one element of order $2$ then $x=e$.   What I've done so far: (#1 is just for illustration, There should be at least $3$ such elements)   $G$ has an even number of elements with order $&gt;2$ (They are paired so: $(a,a^{-1})$ ). And then there are $e$ and $\{b|o(b)=2\}$. Also, if $G$ has at least one element of order 2 then $|G|$ is even (Lagrange). Thus $|\{b|o(b)=2\}|$ must be odd. If there is exactly one element $b$ of order $2$ then $x=b$. That's because $G$ is abelian, and we can write: $x=e\cdot b\cdot(a_1 a_{1}^{-1}\dotsm a_n a_{n}^{-1})=b\cdot(e\dotsm e)=b$. If there are exactly $3$ such elements $a,b,c\in G$, then, as shown above, $x=abc$ and thus $x=e$ (That's because $(abc)^2=a^2b^2c^2=e$ which means $abc\in \{a,b,c,e\}$. If $abc=a$ then $b=c^{-1}=c$ which is false, same goes for $abc=b,abc=c$.)   I haven't managed to find a reason why the claim must hold for $5, 7, ...$ (i.e. All other odd integers). Does anyone have an idea?  Thanks in advance. Please excuse my English.  edit: Not a canonical answer but a simple one (if such even exists). Is it proper to use "the" before the name of a government organization? I've been working on the Android SDK platform, and it is a little unclear how to save an application's state. So given this minor re-tooling of the 'Hello, Android' example:  package com.android.hello;  import android.app.Activity; import android.os.Bundle; import android.widget.TextView;  public class HelloAndroid extends Activity {    private TextView mTextView = null;    /** Called when the activity is first created. */   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);      mTextView = new TextView(this);      if (savedInstanceState == null) {        mTextView.setText("Welcome to HelloAndroid!");     } else {        mTextView.setText("Welcome back.");     }      setContentView(mTextView);   } }   I thought it would be enough for the simplest case, but it always responds with the first message, no matter how I navigate away from the app.  I'm sure the solution is as simple as overriding onPause or something like that, but I've been poking away in the documentation for 30 minutes or so and haven't found anything obvious. What steps does a manuscript typically go through from submission to publication (or rejection) in a typical journal? How are these steps referred to, in particular by editorial systems, and how long do they each typically take?  Note that this question is about the typical situation and hence not about:   Journals with an atypical workflow, e.g. those that allow for an instantaneous reviewer–author interaction. Exceptional steps or rare occurrences such as withdrawal or .   This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question. Cannot see Samba configuration tool in the Dash in ubuntu 14.04 After a fresh installation of ubuntu 14.04 (my previous installation has seen to be broken somewhere reading .wmv file with VLC), I've installed Samba GUI tool from the software center.  It briefly appears in the launchpad then disappears. From this time I cannot the see in in the dash.  I've found this in askUbuntu   but the command sudo apt-get install samba samba-common gives me nothing to install.  Lecture des listes de paquets... Fait Construction de l'arbre des dépendances        Lecture des informations d'état... Fait samba est déjà la plus récente version disponible. samba passé en « installé manuellement ». samba-common est déjà la plus récente version disponible. Les paquets suivants ont été installés automatiquement et ne sont plus nécessaires :   kde-l10n-engb kde-l10n-fr Veuillez utiliser « apt-get autoremove » pour les supprimer. 0 mis à jour, 0 nouvellement installés, 0 à enlever et 8 non mis à jour.   The following guide  has no result either.  Any idea ?  Laurent06000 How to find the inverse modulo $m$? has played the role of Wolverine as a major character in various X-Men films since 2000 and contributed highly to the brand of the X-Men movie series. But is he playing the Wolverine character for the last time in Logan?  I am getting to know from my friends that  is the last movie in which he is playing Wolverine and they all say that this is his last contracted film.  Are these rumors true? Is there any official information that confirms that this is Hugh Jackman's last movie as Wolverine? I want to install OpenOffice. What can I do to install it on my computer? I've a file named addresses.txt :  address1@domain.com address2@domain.com address3@domain.com   I'd like to echo "address1@domain.com.html" using for loop. Here's what I did :  cat addresses.txt | while read address do echo "${address}.html" done   Here's the result :  .htmlss1@domain.com .htmlss2@domain.com .htmlss3@domain.com   Same result if I add a space between the variable and ".html"  What am I miss ?  Thanks Avoiding labeling features if overlapped by another layer in QGIS? With QGIS 2.12.2, how can I set up layer labeling to avoid placing labels where features from another layer already exist?  For example, if I have a stream/river polyline layer that contains lake "centerlines", and I place a "lake" polygon layer above it in the drawing order, I don't want the river layer to place a label inside the lake.  Instead, I would rather have the river labeled outside of the lake (as needed).  That way, I can place labels from the lakes layer and I don't run into label collisions.  Here is an example, where (I have intentionally put the lines on top for visual purposes) what I am hoping to achieve is no river center-line labels shown inside the lake polygon: How to down-weight older data in time series regression In a regression fit of vectors varying with time $t$ $\qquad y \sim [x_t\ x_{t-1}\ x_{t-2}\ ...] \cdot [c_t\ c_{t-1}\ c_{t-2} \ ...] $ , how can one down-weight the older $x_t$ to model "older is less relevant" (than the regression gives) ? Say that rows in data matrix $X$ are observables (stocks, market segments ...) and columns are times. Correct me,   weights rows; how does one weight columns, times ?  Added: Down-weighting older data in time series looks complex, much more so than linear least squares with i.i.d. errors in rows (observations) -- just divide through by $\sigma_i$; or classification  with i.i.d. errors in columns (e.g. features) -- just centre each column. Can anyone say either   yes, I downweight time series; here are some examples on the web no: down-weighting time series is complex, not for novices.   (  discussed this question 10 years ago, mentioning Kalman filters and hierarchical Bayes, but with no examples.) How should we treat questions that are, or have seeds of, evil or malicious purposes and actions, such as writing spambots and malware?    Should they be answered like regular "everybody keeps their pants on" questions? Or should there be some other type of response to this bad behaviour lot? I know I can become root (super user) via the su command but I have to authorize it after entering the commands. Is there a way I can become root and authorize (with password) in one line Do I need to license fonts included with my OS? Is it better to have an ErrorDocument 404 redirect back to the homepage or a standard 404 error page? I have a bunch of magnets (one of those game-board thingies) given to me when I was a school-going lad over 20 years ago, and the magnets feel just as strong as it was the day it was given.   As a corollary to this question , is there a way to determine how long a permanent magnet will remain a magnet?   Addendum: Would two magnets remain a magnet for a shorter duration if they were glued in close proximity with like poles facing each other? What is DOCTYPE? Is drawing multiple cards an atomic action? Is drawing multiple cards an atomic action, or do effects triggered by drawing a card trigger for each card drawn instead?  Consider , which reads:     Whenever a player draws a card, Spiteful Visions deals 1 damage to that player.   If a player were to be compelled to draw more than one card, would that player be dealt the damage all at once, or one at a time? For example, how many times would  need to be activated to prevent all damage?  Furthermore, if there exist additional effects that are triggered by damage dealt in this way, are such effects resolved together atomically or is each resultant effect resolved individually?    How about tutors, or other cards not using the word 'draw', eg:      If you would draw a card, look at the top three cards of your library instead. Put one of those cards into your hand and the rest on the bottom of your library in any order. Why can't a class extend its own nested class in C#? For example:  public class A : A.B {     public class B { } }   Which generates this error from the compiler:     Circular base class dependency   involving 'A' and 'A.B'   I always figured a nested class behaved just like a regular class except with special rules concerning accessing the outer class's private members, but I guess there's some implicit inheritance occurring between the two classes?