Getting x value from a string
How to evaluate a math expression given in string form?
Local polynomial regression: Why does the variance increase monotonically in the degree? How can I show that the variance of local polynomial regression is increasing with the degree of the polynomial (Exercise 6.3 in Elements of Statistical Learning, second edition)?  This question has been asked  but the answer just states it follows easliy.  More precisely, we consider $y_{i}=f(x_{i})+\epsilon_{i}$ with $\epsilon_{i}$ being independent with standard deviation $\sigma.$  The estimator is given by  $$ \hat{f}(x_{0})=\left(\begin{array}{ccccc} 1 &amp; x_{0} &amp; x_{0}^{2} &amp; \dots &amp; x_{0}^{d}\end{array}\right)\left(\begin{array}{c} \alpha\\ \beta_{1}\\ \vdots\\ \beta_{d} \end{array}\right) $$ for $\alpha,\beta_{1},\dots,\beta_{d}$ solving the following weighted least squares problem $$ \min\left(y_{d}-\underbrace{\left(\begin{array}{ccccc} 1 &amp; x_{1} &amp; x_{1}^{2} &amp; \dots &amp; x_{1}^{d}\\ \vdots\\ 1 &amp;  &amp;  &amp;  &amp; x_{n}^{d} \end{array}\right)}_{X}\left(\begin{array}{c} \alpha\\ \beta_{1}\\ \vdots\\ \beta_{d} \end{array}\right)\right)^{t}W\left(y-\left(\begin{array}{ccccc} 1 &amp; x_{1} &amp; x_{1}^{2} &amp; \dots &amp; x_{1}^{d}\\ \vdots\\ 1 &amp;  &amp;  &amp;  &amp; x_{n}^{d} \end{array}\right)\left(\begin{array}{c} \alpha\\ \beta_{1}\\ \vdots\\ \beta_{d} \end{array}\right)\right) $$ for $W=\text{diag}\left(K(x_{0},x_{i})\right)_{i=1\dots n}$ with $K$ being the regression kernel. The solution to the weighted least squares problem can be written as $$ \left(\begin{array}{cccc} \alpha &amp; \beta_{1} &amp; \dots &amp; \beta_{d}\end{array}\right)=\left(X^{t}WX\right)^{-1}X^{t}WY. $$ Thus, for $l(x_{0})=\left(\begin{array}{ccccc} 1 &amp; x_{0} &amp; x_{0}^{2} &amp; \dots &amp; x_{0}^{d}\end{array}\right)\left(X^{t}WX\right)^{-1}X^{t}W$ we obtain $$ \hat{f}(x_{0})=l(x_{0})Y $$ implying that  $$ \text{Var }\hat{f}(x_{0})=\sigma^{2}\left\Vert l(x_{0})\right\Vert ^{2}=\left(\begin{array}{ccccc} 1 &amp; x_{0} &amp; x_{0}^{2} &amp; \dots &amp; x_{0}^{d}\end{array}\right)\left(X^{t}WX\right)^{-1}X^{t}W^{2}X\left(X^{t}WX\right)^{-1}\left(\begin{array}{ccccc} 1 &amp; x_{0} &amp; x_{0}^{2} &amp; \dots &amp; x_{0}^{d}\end{array}\right)^{t}. $$ My approach: An induction using the formula for the inverse of a block matrix but I did not succeed.  The paper  by D. Ruppert and M. P. Wand derives an asymptotic expression for the variance for $n\rightarrow\infty$ in Theorem 4.1 but it is not clear that is increasing in the degree. Getting full JS autocompletion under Sublime Text Currently I have a script.sh file with the following content:  #!/bin/bash wget -q http://exemple.com/page1.php; wget -q http://exemple.com/page2.php; wget -q http://exemple.com/page3.php;   I want to execute the commands one by one, when the previous finishes. Am I doing it in the right way? I've never worked with Linux before and tried to search for it but found no solutions. Lightning component quick action - send parameters to the lightning component I have a lightning component that is available for use as lightning component quick action. I need to use this component from various object actions, for example, I will add a lightning component quick action to account object and to contact object. Now on the lightning component itself, I want to know if it was invoked from the account object or from the contact object, but I cannot find a way to do that. I have found a way to get the record Id by adding &lt;aura:attribute name=&quot;recordId&quot; type=&quot;String&quot; /&gt; (see code snippet below) It is working but not good enough. What I really need is to send a parameter from the lightning component quick action invocation:  And get it in my component: &lt;aura:component implements=&quot;force:lightningQuickAction,force:hasRecordId,flexipage:availableForAllPageTypes&quot;&gt;     &lt;aura:attribute name=&quot;recordId&quot; type=&quot;String&quot; /&gt;     &lt;aura:attribute name=&quot;param&quot; type=&quot;String&quot;/&gt; &lt;/aura:component&gt;  Is this possible? And if not - any workaround for achieving that? Preventing itemize environment to insert initial vertical space Extend a language with additional keywords? Is there any way to hide your Steam status from others? Is there any way to prevent others from seeing your Steam status without removing them as a friend?   Let's say I want to play Borderlands 2 without letting some friends know. Is there any way to hide my status to prevent them from knowing I'm playing it?  Basically, what I'm asking if Steam has an "Appear Offline" option. Installing Wi-Fi driver for Realtek Semiconductor RTL8723DE Device [10ec:d723] How do I install Wi-Fi drivers for Realtek RTL8723DE device in Ubuntu 16.04?  lspci -v | grep -i network 02:00.0 Network controller: Realtek Semiconductor Co., Ltd. Device d723 reference variable In some text it is given that we can't assign constant values to a reference variable. When I executed such a program I could do it. Is there any condition we can't assign a constant value to a reference variable? How to run long time process on Udev event? I want to run a ppp connection when my USB modem is connected, so I use this udev rule:  ACTION=="add", SUBSYSTEM=="tty", ATTRS{idVendor}=="16d8",\     RUN+="/usr/local/bin/newPPP.sh $env{DEVNAME}"  (My modem appears in /dev as ttyACM0)  newPPP.sh:  #!/bin/bash /usr/bin/pon prov $1 &gt;/dev/null 2&gt;&amp;1 &amp;   Problem:  The udev event fires, and newPPP.sh is running, but newPPP.sh process is killed after ~4-5s. ppp does not have time to connect (its timeout is 10s for dial up).  How can I run a long time process, that will not be killed?  I tried using nohup, but it didn't work either.  System: Arch Linux  Update  I found a solution , thanks to .  I use at now to run my job detached from udev process.  But the one question remains unanswered: Why do nohup and &amp; not work? Is it really possible to break the speed of light by flicking your wrist with a laser pointer? I'm a Windows/Mac/Ubuntu and Android user, so I know what I'm talking about, when I say: How do I open binary image files? (.img) They just won't open, on any OS…  I'm an Android dev… I'm currently working on a ROM, (I also program, using Windows) but I need to extract files, from .img files. I've converted them to .ext4.img but they just aren't recognized by Linux (Definitly not by Android), by Mac OS or Windows. In other words, I can't open, extract or mount them.  Can anyone help me? I'm kinda confused… In Java, you can qualify local variables and method parameters with the final keyword.  public static void foo(final int x) {   final String qwerty = "bar";  }   Doing so results in not being able to reassign x and qwerty in the body of the method.  This practice nudges your code in the direction of immutability which is generally considered a plus. But, it also tends to clutter up code with "final" showing up everywhere. What is your opinion of the final keyword for local variables and method parameters in Java? "A few" takes a singular or plural verb in present simple tense? Does "a few" take a singular or plural verb in present simple tense?        A few men lifts the table.   A few men lift the table.   A few frogs jumps out of the lake.   A few frogs jump out of the lake.      I have searched the same question in google, but I see both answers. Which one is correct? How come "a few" is plural? Even though it refers to many, "a" makes "few" a singular, so it should take a singular verb, right?  Should I always put "a" in front of "few"? For example, are the following correct?        Few men lift the table.   Few frogs jump out of the lake. Enumerate paragraphs and subparagraphs like sections but with letters I'm using pandoc and in my template.tex exists this code to make the paragraphs and subparagraphs to behave like sections.  % Redefines (sub)paragraphs to behave more like sections \ifx\paragraph\undefined\else \let\oldparagraph\paragraph \renewcommand{\paragraph}[1]{\oldparagraph{#1}\mbox{}} \fi \ifx\subparagraph\undefined\else \let\oldsubparagraph\subparagraph \renewcommand{\subparagraph}[1]{\oldsubparagraph{#1}\mbox{}} \fi   This code generate number like this:  1. chapter  1.1 section  1.1.1 subsection  1.1.1.1 subsubsection  1.1.1.1.1 paragraph  1.1.1.1.1.1 subparagraph   How to change this code to enumerate with letter like this:  1. chapter  1.1 section  1.1.1 subsection  1.1.1.1 subsubsection  1.1.1.1.a paragraph  1.1.1.1.a.a subparagraph Shell programming temp=$1 vs temp=1 What's the difference between temp=$1 and temp=1? Why do I need the dollar sign?  For example:   #!/bin/bash  temp=$1 cell=$((($temp-32)*5/9))  echo $cell Is it legal to study while on a tourist Schengen visa? If, say, you acquired a 90-day tourist Schengen visa, would it be legal to use it for the purpose of visiting a language course or a university class? Or do you have to apply for a special education visa if you have such intents?  Answers linking to official EU pages on that matter would be highly appreciated :) How to batch resize an image and create multiple sizes (with Photoshop)? I want to batch resize an image in multiple sizes with Photoshop.  The sizes are most of the time the same so I would like to have profiles for a set of fixed sizes. Ideally I just need to open my source image and click on "Batch Profile #1" and then Photoshop is creating/saving X different sizes of that image as an output in a specific folder.  This is what i want: Invoking JavaScript code in an iframe from the parent page Basically, I have an iframe embedded in a page and the iframe has some  routines I need to invoke from the parent page.  Now the opposite is quite simple as you only need to call parent.functionName(), but unfortunately, I need exactly the opposite of that.  Please note that my problem is not changing the source  of the iframe, but invoking a function defined in the iframe. Moving app to production mode in Symfony 2