I want to install:  add-apt-repository ppa:ricotz/testin   It is showing:  The program add-apt-repository is currently not installed. You can install it by typing: sudo apt-get install python-software-properties   What should I do now?
The server version of Ubuntu does not have the  command. How can I add a  (PPA) to the server without this command?
Take as an example the well-known . In the original paper, the regression model was used to model the amount people were willing to pay for improved air quality.  But the 'people' whose behaviour was being modelled was never specified. Presumably, it was not limited to 'residents of Greater Boston'. Only implausibly would it be 'humans anywhere on the planet'. Nor, 'all US residents'.   So what inference are we invited by the authors to draw about the scope they intend for their theory? Perhaps 'all residents of large US metro areas'. But - what about other First World metro areas? The first two sections of the Boston paper scrupulously avoid any reference which might suggest that they had a particular 'population' to which their 'sample' was to apply.  There is also the dimension of time - the data came from the 70s, whereas the theory is has no time limitations spelt out.  Plus - going back to first principles - how could the Boston data be treated as a sample of a population including, say, the Chicago metro area when no data from the Chicago area was considered?   Besides, lots of the covariates in the Boston regression weren't samples at all, but totals - so, for example, the proportion of blacks was supplied from census stats.  My question: how can we conceive the Boston data as supporting the geographically unlimited propositions in the paper? Is there a mathematical way of showing equivalence or approximation of the Boston data analysis to other cities? Or is it just assumed as a matter of common sense - such that the paper's authors would be amazed to think anyone could have any doubts on the matter? Why, logically, is proof by contradiction valid? I'm subscribed to the Ubuntu Security Notes, so everytime that I receive an e-mail, a new update is avalable.  But in the last update, they wrote something in the end that I coudn't undertand much, so can anyone please tell me what does that means?  ATTENTION: Due to an unavoidable ABI change the kernel updates have been given a new version number, which requires you to recompile and reinstall all third party kernel modules you might have installed. If you use linux-restricted-modules, you have to update that package as well to get modules which work with the new kernel version. Unless you manually uninstalled the standard kernel metapackages (e.g. linux-generic, linux-server, linux-powerpc), a standard system upgrade will automatically perform this as well.   I tried to ask to my friend (who also uses Linux), but he don't know much about kernel. I tried this way, I only need to know if this is correct or if there are better ways to solve this:  $2^{1000}$ does not have a factor of $5$ obviously therefore we can assume  $$ 10^{m} &lt; 2^{1000} &lt; 10^{m+1}$$ for some  $m$   Assume $ k = 2^{1000}$, then take log on both sides $\log k = 1000  \log 2 \approx 301.02999 &gt; 301$  Therefore $2^{1000}$ has $302$ digits. extract the 4th column from a csv file using unix command I have a csv file formatted as below.  "col1","col2","col3","col4" "1","text1","&lt;p&gt;big       html      text&lt;/p&gt; ","4th column" "2","text2","&lt;p&gt;big2       html2      text2&lt;/p&gt; ","4th column2"   I want to extract the 4th column using.  I think that awk is the best tool for this ( let me know if I am wrong). I tried this   awk -F, '{print $4}' myFile.csv    but it fails.  I think because the 3rd column is multiline one.  How can I use awk or any other unix command to extract the 4th column.  I am looking for an efficient solution since my real file is big (> 2GB) Interpretation of the rating of a real transformer The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both.  To clarify further, suppose to solve for certain characteristics of this transformer like primary current and secondary current i use the equivalent circuit equation of the transformer referred to the primary side as:  Vp = aVs + Req*Ip + jXeq*Ip  Then what should i use for Vp or Vs in the above equation looking at the rating of the transformer.  In the above equation looking at the rating data given above is Vp= 2300 or Vs = 230 ?As mentioned earlier the transformer is mentioned to be real. Max dimension of a subspace of singular $n\times n$ matrices I am sure the answer to this is (kind of) well known. I've searched the web and the site for a proof and found nothing, and if this is a duplicate, I'm sorry.  The following question was given in a contest I took part. I had an approach but it didn't solve the problem.     Consider $V$ a linear subspace of the real vector space $\mathcal{M}_n(\Bbb{R})$ ($n\times n$ real entries matrices) such that $V$ contains only singular matrices (i.e matrices with determinant equal to $0$). What is the maximal dimension of $V$?   A quick guess would be $n^2-n$ since if we consider $W$ the set of $n\times n$ real matrices with last line equal to $0$ then this space has dimension $n^2-n$ and it is a linear space of singular matrices.  Now the only thing there is to prove is that if $V$ is a subspace of $\mathcal{M}_n(\Bbb{R})$ of dimension $k &gt; n^2-n$ then $V$ contains a non-singular matrix. The official proof was unsatisfactory for me, because it was a combinatorial one, and seemed to have few things in common with linear algebra. I was hoping for a pure linear algebra proof.  My approach was to search for a permutation matrix in $V$, but I used some 'false theorem' in between, which I am ashamed to post here. Show that if $a^{n-1} \equiv 1 \pmod{n}$ for all $a$ such that $\gcd(n,a) = 1$, then $a^{n} \equiv a \pmod{n}$ for all $a$. In Burton's Elementary Number Theory, when introducing absolute pseudoprimes (also called Carmichael numbers), the author states that they are composite numbers $n$ such that $a^{n-1} \equiv 1 \pmod n$ for all integers $a$ with $\gcd(a,n) = 1$.   When showing that 561 is an absolute pseudoprime, he then concludes that $a^{561} \equiv a \pmod{561}$ for all $a$.   I searched a bit on the internet, and it seems that these two are actually equivalent definitions of a Carmichael number. However I have not been able to find a proof; the fact that the implication in the title of the post is stated so plainly in my textbook makes me think it is quite simple to see, but I can't seem to understand the argument. Find the value of : $\cos x \cos 2x...\cos 999x$ given that $x=\frac {2\pi}{1999}$ Given $x=\frac {2\pi}{1999}$  Find the value of $$\cos x \cos 2x \cos 3x ...\cos 999x$$  So I tried expanding $\sin {2000x}=2\sin 1000x \cos 1000x$  Then rewriting  $\cos 1000x= \cos {(999x+x)}$   No luck so far. how do I get my code to use the value of the $HOME variable? I'm trying to put together a generic script that will check the existence of several key directories for various users on different servers. Additionally, I want to leverage each user's $HOME variable.  For eg, let's say this were true:   on server 1: jdoe's home is /home/jdoe  on server 2: jdoe's home is /opt/jdoe2 server 3 hasn't been built yet; we won't know where they build his $HOME until the server is built. on server 4: mysql's home is /opt/home/mysql   This is what I have for my important directories (ordered from most to least impt):  $ cat mylist.txt $HOME/most_impt_dir1 $HOME/most_impt_dir2 $HOME/most_impt_dir3 $HOME/misc $HOME/junk   ...I want to find the most impt dir owned by this user.   Here's what I'm trying:  for i in `cat mylist.txt` do    if [[ -O $i ]] &amp;&amp; [[ -d $i ]]; then     echo "found it: $i"     break   else     echo "$i is not it."   fi  done   The above code does not work for anything in my list because it is literally checking for dirs beginning with $HOME. How do I get my code to use the value of the user's $HOME variable? I believe that the set of all $\mathbb{R\to R}$ continuous functions is $\mathfrak c$, the . However, I read in the book &quot;Metric spaces&quot; by Ó Searcóid that set of all $[0, 1]\to\mathbb{R}$ continuous functions is greater than $\mathfrak c$:  &quot;It is demonstrated in many textbooks that $\mathbb{Q}$ is countable, that $\mathbb{R}$ is uncountable, that every non-degenerate interval is uncountable, that the collection of continuous functions deﬁned on  $[0,1]$ is of a greater cardinality than $\mathbb{R}$, and that there are sets of greater and greater cardinality.&quot;  I understand that (via composition with the continuous function $\tan$ or $\arctan$) these sets of continuous functions have the same cardinality. Therefore, which claim is correct, and how do I prove this? Pure virtual destructor in C++ While building things I want to see the overlays from other modes so I can make better decisions. Can I lock an overlay somehow?  For example: When building roads I want to see the natural resources overlay. When zoning I want to see the wind overlay When should I use "a" vs "an"? I have studied that every normed space $(V, \lVert\cdot \lVert)$ is a metric space with respect to distance function  $d(u,v) = \lVert u - v \rVert$, $u,v \in V$.   My question is whether every metric on a linear space can be induced by norm? I know answer is  no but I need proper justification.   Edit: Is there any method to check whether a given metric space is induced by norm ?  Thanks for help User's suspension period has expired, but they're still suspended? I came across a user with a notification that states:     This account is temporarily suspended network-wide. The suspension period ends on Dec 2 '18 at 2:35.   Screencap for posterity:    Unless this user is  (in which case the full year should be shown, or at least a tooltip), it seems like they should have been unbanned 4 months ago. Are split infinitives grammatically incorrect, or are they valid constructs? Mark's generosity in this crisis seems to more than make up for his earlier stinginess.   Should those sentences always be avoided, or are there cases where they are valid? Is Poly1305 an information-theoretically secure MAC? ls: cannot access .gvfs: Permission denied Can a multiclass sorcerer make spell slots for their other class using sorcery points?  For example: can a multiclassed sorcerer 3 / warlock 1 use Flexible Casting to create a warlock spell slot?