I want to install ns2.35 on Ubuntu 14.04. When I implement this command:  $ sudo apt-get install tcl8.5-dev tk8.5-dev Reading package lists... Done Building dependency tree   Reading state information... Done E: Unable to locate package tcl8.5-dev E: Couldn't find any package by regex 'tcl8.5-dev' E: Unable to locate package tk8.5-dev E: Couldn't find any package by regex 'tk8.5-dev'   What should I do for resolving this problem?
When I try to install any package through the command line, I get an error.   $ sudo apt-get install &lt;package&gt; Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package &lt;package&gt;   Can anyone help me on this?
What is the closure of an open ball $B_X(\mathbf{a},r)$ in $X=\mathbb{R}^n$? Suppose we have the open ball $B_{X}(\mathbf{a},r)$ and the closed ball $\bar{B}_{X}(\mathbf{a},r)$ of radius $r$ about $\mathbf{a}\in\mathbb{R}^n=X$ with the Euclidean metric $d_2$.  What is the closure of an open ball $B_{X}(\mathbf{a},r)$ in $(\mathbb{R}^n,d_2)$?  First, I have defined the sets like this:  $$B_X(\mathbf{a},r)=\{\mathbf{y}\in\mathbb{R}^n:d_2(\mathbf{a},\mathbf{y})&lt;r\}$$ $$\bar{B}_X(\mathbf{a},r)=\{\mathbf{y}\in\mathbb{R}^n:d_2(\mathbf{a},\mathbf{y})\le r\}$$  Then, let $U=B_X(\mathbf{a},r)$ and claim the closure is $$\bar{U}=\{\mathbf{x}\in\mathbb{R}^n:\exists (\mathbf{x}_n)\in U\text{s.t}~\mathbf{x}_n\to \mathbf{x}\}=\bar{B}_X(\mathbf{a},r).$$  Since closed balls are closed then we have $$\bar{U}\subset\bar{B}_X(\mathbf{a},r).$$  But, how can I prove the other direction $\bar{B}_X(\mathbf{a},r)\subset\bar{U}$?  Since it's a containment argument I know that I have to take any element from $\bar{B}_X(\mathbf{a},r)$ and show it is in $\bar{U}=\{\mathbf{x}\in\mathbb{R}^n:\exists (\mathbf{x}_n)\in U\text{s.t}~\mathbf{x}_n\to \mathbf{x}\}$.  But I do not know how to get an expression for $\mathbf{x}_n$.  I would appreciate any help. How do you auto resize cells in Excel? Category Theory textbook (learning through guided discovery Dummit and Foote) How to format hard drive I'm looking for the antonym of -cide (as in suicide, pesticide, etc.). Essentially the ending to words that would mean "to create or embrace". Call to a member function on a non-object So I'm refactoring my code to implement more OOP.  I set up a class to hold page attributes.  class PageAtrributes  {   private $db_connection;   private $page_title;      public function __construct($db_connection)      {         $this-&gt;db_connection = $db_connection;         $this-&gt;page_title = '';     }      public function get_page_title()     {         return $this-&gt;page_title;     }      public function set_page_title($page_title)     {         $this-&gt;page_title = $page_title;     } }   Later on I call the set_page_title() function like so  function page_properties($objPortal) {         $objPage-&gt;set_page_title($myrow['title']); }   When I do I receive the error message:     Call to a member function set_page_title() on a non-object   So what am I missing? This is my last homework problem and I've been looking at it for a while. I cannot nail down what is wrong with this proof even though its obvious it is wrong based on its conclusion. Here it is:     Find the flaw in the following bogus proof by strong induction that   for all $n \in \Bbb N$, $7n = 0$.      Let $P(n)$ denote the statement that $7n = 0$.      Base case: Show $P(0)$ holds.      Since $7 \cdot 0 = 0$, $P(0)$ holds.      Inductive step: Assume $7·j = 0$ for all natural numbers $j$ where $0 \le j \le k$ (induction hypothesis). Show $P(k + 1)$: $7(k + 1) = 0$.      Write $k + 1 = i + j$, where $i$ and $j$ are natural numbers less than $k + 1$.  Then, using the induction hypothesis, we get $7(k + 1) = 7(i + j) = 7i + 7j = 0 + 0 = 0$. So $P(k + 1)$ holds.      Therefore by strong induction, $P(n)$ holds for all $n \in \Bbb N$.   So the base case is true and I would be surprised if that's where the issue is.  The inductive step is likely where the flaw is. I don't see anything wrong with the strong induction declaration and hypothesis though and the math adds up! I feel like its so obvious that I'm just jumping over it in my head. Difficulty in creating macro '\newcommand' for the beginning and end of frames in Beamer Hide page numbering but retain header/footer I would like to remove page numbering on a specific page. However, the header and footer should remain intact. If I try:  \thispagestyle{empty}   The header and footer disappear. What is the recommended way of removing just the page number? Help me understand Bayesian prior and posterior distributions In a group of students, there are 2 out of 18 that are left-handed. Find the posterior distribution of left-handed students in the population assuming uninformative prior. Summarize the results. According to the literature 5-20% of people are left-handed. Take this information into account in your prior and calculate new posterior.    I know the beta distribution should be used here. First, with $\alpha$ and $\beta$ values as 1? The equation I found in the material for posterior is   $$\pi(r \vert Y ) \propto r^{(Y +−1)} \times (1 − r)^{(N−Y +−1)} \\ $$  $Y=2$, $N=18$  Why is that $r$ in the equation? ($r$ denoting the proportion of left-handed people). It is unknown, so how can it be in this equation? To me it seems ridiculous to calculate $r$ given $Y$ and use that $r$ in the equation giving $r$. Well, with the sample $r=2/18$ the result was $0,0019$. The $f$ should I deduce from that?  The equation giving an expected value of $R$ given known $Y$ and $N$ worked better and gave me $0,15$ which sounds about right. The equation being $E(r | X, N, α, β) = (α + X)/(α + β + N)$ with value $1$ assigned to $α$ and $β$. What values should I give $α$ and $β$ to take into account prior information?  Some tips would be much appreciated. A general lecture on prior and posterior distributions wouldn't hurt either (I have vague understanding what they are but only vague) Also bear in mind I'm not very advanced statistician (actually I'm a political scientist by my main trade) so advanced mathematics will probably fly over my head. Proving that $G$ is a group if $a*x=b$ and $y*a=b$ have solutions. (Reference : Fraleigh, A first course in abstract algebra)     Prove that a nonempty set $G$, together with an associative binary operation * on $G$ such that $a*x=b$ and $y*a=b$ have solutions in G, $\forall a,b\in G$, is a group.   Because * is an associatie operation, we have to prove that: there exists $e\in G$ such that $e*a=a=a*e$ for any $a\in G$, and that for any $a\in G$ there exists $\alpha \in G$ such that $a*\alpha=e=\alpha *a$.  This is very confusing, first I tried to prove the identity exists. If we consider a=b, then $a*x=a=y*a$, and because of the hypothesis $x,y\in G$ always exists, now we have to show that $x=y$, but I just can't do this with out inverses, so I tried to prove that the inverses exists, however I have no idea how the identity looks like, I'm stuck.  And I tried to get unstuck, so I thought particular cases, first if $G$ had only one element, then what would happend if it had just two elements... but I remembered that we don't know if G is finite or not, and I think this makes things a little bit more complicated.  What can I do? Handling circular entity references with Migrate I am using  on a Drupal 6 to Drupal 7 migration right now.  I have three types: type1, type2, type3.  Each of the three types has a entityreference field on it, which is configured to be able to point to all three types.  This means that there can be circular references, and when a particular node is being migrated, the destination node may not exist yet and could potentially be any of the three types.  My migration class looks like this:  class MyNodeMigration extends DrupalNode6Migration {   public function __construct(array $arguments) {     parent::__construct($arguments);      $this-&gt;addFieldMapping('field_legacy_nid', 'nid');      $this-&gt;addFieldMapping('field_the_reference', 'field_the_reference')       -&gt;sourceMigration(array('type1', 'type2', 'type3');   } }  $node_arguments = array(   array(     'class_name' =&gt; 'MyNodeMigration',     'description' =&gt; 'type1',     'machine_name' =&gt; 'type1',     'source_type' =&gt; 'type1',     'destination_type' =&gt; 'type1',     'dependencies' =&gt; array('roles', 'users'),   ),    array(     'class_name' =&gt; 'MyNodeMigration',     'description' =&gt; 'type2',     'machine_name' =&gt; 'type2',     'source_type' =&gt; 'type2',     'destination_type' =&gt; 'type2',     'dependencies' =&gt; array('roles', 'users'),   ),    array(     'class_name' =&gt; 'MyNodeMigration',     'description' =&gt; 'type3',     'machine_name' =&gt; 'type3',     'source_type' =&gt; 'type3',     'destination_type' =&gt; 'type3',     'dependencies' =&gt; array('roles', 'users'),   ), );  $common_node_arguments = $common_arguments + array(   'user_migration' =&gt; 'users', );  foreach ($node_arguments as $arguments) {   $arguments = array_merge_recursive($arguments, $common_node_arguments);    Migration::registerMigration($arguments['class_name'], $arguments['machine_name'], $arguments); }   When I run the migrations, most nodes are fine, but I get a decent amount of Stubs (*) created.  Some of the destination nodes have the entityreference pointing to these Stub nodes.  The source nodes are fine.  What I have uncovered is that the bundle on the destination nodes that are being made as stubs are incorrect, and look like they are all type1.  A node of the proper type does end up being created, but it never gets set as the entityreference target.  Another way to explain this is that I end up with   node: nid=123, type=type1 node: nid=234, type=type1, field_the_reference=123 node: nid=345, type=type2   where it should be   node: nid=234, type=type1, field_the_reference=345 node: nid=345, type=type2   How do I handle this situation?  (*): a "Stub" in the context of this question here refers to a node which is created for the purpose of being a reference target, but does not get its data initially. The term is used throughout the Migrate documentation and source code. Why does Gandhi want to nuke me? Different civilizations obviously have different priorities. For example, Gandhi always seems to rush nuke technology and the Mongols will most likely start invading and spread like mad. Are these variables public knowledge? Can you tell by who you are playing what strategy they will adopt during the game? Does Wolfram Mathworld make a mistake describing a discrete probability distribution with a probability density function? Potato Power. Self sustaining medium using a living potato plant possible? I saw a lot of times claims that they have to be exhaustive (the examples in such books were always set in such way, that they were indeed), on the other hand I also saw a lot of times books stating they should be exclusive (for example $\mathrm{H}_{0}$ as $\mu_1=\mu_2$ and $\mathrm{H}_{1}$ as $\mu_1&gt;\mu_2$) without clarifying the exhaustive issue. Only before typing in this question I found somewhat stronger statement on the  -- "The alternative need not be the logical negation of the null hypothesis".  Could someone more experienced explain which is true, and I would be grateful for shedding some light on the (historical?) reasons for such difference (the books were written by statisticians after all, i.e. scientists, not philosophers). explicit formula for recurrence relation $a_{n+1}=2a_n+\frac{1}{a_n}$ I'm looking for a way of saying “having amorous affairs”. Ideally it should indicate a married man fooling around with younger women, and the expression should be informal, humorous, in low register but yet not rude. Maintenance plan for creating transaction log backups I have a database that is set to the 'Full' recovery model, and I'm creating a maintenance plan to backup the Transaction Log every 15 minutes. A full backup is then taken once every 24 hours.  I was wondering: will the maintenance plan for the transaction logs create a lot of different files every 15 minutes, or will it by default append to the same file for 24 hours?  Also: what is preferred? I couldn't find anything on this subject (or maybe I was Googling the wrong words).  Thanks for any pointers anyone can give me.  EDIT: I also see that the checkmark "Verify backup integrity" is OFF by default. Is there a risk with turning it on? It seems to be that it should be on by default, so is there a reason for not using this? How to add percent sign to NSString