How would one write down this equation in Latex? What kind of font is used for l and nu?
I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?
Column validation for US phone number format Finding an expression for $\tan (a+ b + y)$ which involves only $\tan a, \tan b,$ and $\tan y$. How to find this ?   I'm stuck at $1$ and how to $1$ to change the tangent associated with a,b or c.  I meant this ,everybody.  $\frac{tan(a)+tan(b)+tan(y)−tan(a)tan(b)tan(y)}{1−tan(a)tan(b)−tan(a)tan(y)−tan(b)tan(y)}$ Pacf lag axe , is not an integer I'm trying to use ARIMA process to predict the behaviour of a time series, the probleme I face is that I can't get the order of each component of ARIMA, the lag is between 0 and 1, same goes for the acf. The time series has no tendency, and I guess no seasonality.     My question is : Does this mean that ARIMA orders are all 0s, and if so, is the HoltWinters a good (or the best) solution for modelling this kind of TS ? I'm pretty new to this and this is my first question here, any help would be greatly appreciated.  So basically what I want to achieve is a floor material as seen in this photo...    ...the reflections are very crisp but dim.  With a glossy shader I get the following results:    First picture: reflections are blurry  Second picture: roughness of the material looks right but reflection is bright red  Third picture: If tinted in any other color than white, it seems to produce the result I want. Reflection is sharp and gets tinted blue. What I need is the reflection to be tinted white.  Thanks for any help. I have 100 files with 57,816 rows each.I want to do an outer join of these files by merging on basis of the common column.  I am using R programming for this but this is very slow.  fileList &lt;- list.files(, pattern=".txt") pm_list=lapply(fileList, read.table) merged_pm=merge_all(pm_list, by = "gene_short_name")   Is there any quick way to do this in bash? The other method that I can use is SQL but I have to create 100 tables first and then load them up before join,which is not very efficient way to do.  The number of rows are equal in each file, thats why I want to merge  based on common column and can't use cbind from R as the constants in the common column are a bit up and down in different files and not present at same location in each file.Below are two sample files.I want to join based on 'gene_short_name'  gene_short_name FPKM56  MT-TF   0.90 MT-TV   0 MT-RNR1 310.015 MT-TL1  0 MT-TM   0   File 2 is below:  gene_short_name FPKM53  MT-TF   0 MT-TV   0.344 MT-TM   0.10 MT-TL1  0 MT-RNR1 0 MT-ND2  158.332 Troubleshooting for biber I'm trying to switch from BibTeX to biber and ran into the problem that biber does not produce any output file. I noticed several questions about problems with biber e.g.,            ,                       But none of them helped me in my particular situation (which was actually just an old version of biber somewhere in the path of my OS). Since I also noticed that several questions regarding problems with biber were closed as too localized since the underlying problem was due to formatting of a bib resource or similar simple issues, I would rather like to ask for a general troubleshooting guideline for using biber (since I saw many hints like "check/delete the cache", "check versions of this and that" etc.).  What steps are to be taken and what things (in particular files) to be checked if biber does not produce an output file (and its output on the command line does not directly give you the advice what to do)? Dropping one of the columns when using one-hot encoding My understanding is that in machine learning it can be a problem if your dataset has highly correlated features, as they effectively encode the same information.  Recently someone pointed out that when you do one-hot encoding on a categorical variable you end up with correlated features, so you should drop one of them as a "reference".  For example, encoding gender as two variables, is_male and is_female, produces two features which are perfectly negatively correlated, so they suggested just using one of them, effectively setting the baseline to say male, and then seeing if the is_female column is important in the predictive algorithm.  That made sense to me but I haven't found anything online to suggest this may be the case, so is this wrong or am I missing something?  Possible (unanswered) duplicate: Label rows of a matrix by characters NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [plymouthd:305] I get this error message   NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [plymouthd:305]    on the startup of my system (even with live-cd).  My PC is a dell inspiron 7559 with intel graphic and nvidia.  UPDATE - this issue also happens when attempting to install ubuntu 18.10 using LiveUSB I'm embarking on a new web map project that seeks to display simple geometries (lines, points, polygons) and rasters/basemaps. Ideally, the map will also allow authorized users to add/remove/edit geometries and their attributes.  What are the available options for the storage of data (e.g. SQL Server Spatial)?  What are the available options for the presentation of data (e.g. ArcGIS Server)?  I'm new to web mapping and am attempting to build a solid understanding of the available options and their pros/cons. making a big summation sign How can I make a big summation sign?   ‎\begin{align}‎ ‎\cos x‎ ‎=‎ ‎‎\sum\limits‎_‎{n=0}^{‎\‎‎infty‎} ‎\frac{(ix)^{2n‎}}{(2n)!}‎‎ \end{align}‎   this is the code which I'm using for summation Clarification on maps in Salesforce I know this might be a very basic question but i'm pretty confused by this:  Map&lt;Id,Account&gt; accountWithOpportunities =      new Map&lt;Id,Account&gt;([SELECT Id,(SELECT Id FROM Opportunities) FROM Account]);   I have no clue on to where the Opportunities are relevant at all in this map and how they are stored or can be accessed?   Can anyone clear this out for me? "grey" vs "gray" are both common equally in use? Yesterday I wrote "gray" in the meaning of the color, but my friend corrected me and told me to write "grey". Today I checked in the  and I found that they are both correct for the same meaning. So, now I just have doubt which one of them is more common in use. Why is the direct product of a finite number of nilpotent groups nilpotent? Speed of light when accelerating I'm studying special relativity and saw the 2 postulates of Einstein. The most remarkable one for me is the universal speed of light. Einstein postulated that the speed of light in vacuum is the same for all inertial observers, regardless of the motion of the source. But what if we are accelerating and we are changing from one inertial frame to another, how will we observe the speed of light? Is it still the same? I suggest it's not? Because I alread saw a small introduction to general relativity where the light will bend in a gravitational field and therefore also when you accelerate. So does the speed of light change because it bends? I have a site that is in French and English. I am able to successfully setup so that users can switch back and forth between the two domains to view either language, however I cannot seem to keep users logged in. When they are logged into the english domain and then switch to the french domain they are required to login again. However if they switch back to the english domain they are still logged in.  As an example we'll use www.english-domain.com as the base (default) domain and www.french-domain.com as the secondary domain  In settings.php I have modified the following, however it doesn't seem to be keeping them logged in. Am I missing something?  /**  * Drupal automatically generates a unique session cookie name for each site  * based on its full domain name. If you have multiple domains pointing at the  * same Drupal site, you can either redirect them all to a single domain (see  * comment in .htaccess), or uncomment the line below and specify their shared  * base domain. Doing so assures that users remain logged in as they cross  * between your various domains.  */ $cookie_domain = 'english-domain.com';   Note: That I have also flushed both site and browser cache as well as deleted any cookies left on my machine.  Update:  Here are my language settings: What is the status of existing measurements of the speed of gravity? The Sitemap Paradox We use a  on Stack Overflow, but I have mixed feelings about it.  Web crawlers usually discover pages from links within the site and from other sites. Sitemaps supplement this data to allow crawlers that support Sitemaps to pick up all URLs in the Sitemap and learn about those URLs using the associated metadata. Using the Sitemap  does not guarantee that web pages are included in search engines, but provides hints for web crawlers to do a better job of crawling your site.  Based on our two years' experience with sitemaps, there's something fundamentally paradoxical about the sitemap:  Sitemaps are intended for sites that are hard to crawl properly. If Google can't successfully crawl your site to find a link, but is able to find it in the sitemap it gives the sitemap link no weight and will not index it!  That's the sitemap paradox -- if your site isn't being properly crawled (for whatever reason), using a sitemap will not help you! Google goes out of their way to make :  &quot;We cannot make any predictions or guarantees about when or if your URLs will be crawled or added to our index&quot;  &quot;We don't guarantee that we'll crawl or index all of your URLs. For example, we won't crawl or index image URLs contained in your Sitemap.&quot;  &quot;submitting a Sitemap doesn't guarantee that all pages of your site will be crawled or included in our search results&quot;   Given that links found in sitemaps are merely recommendations, whereas links found on your own website proper are considered canonical ... it seems the only logical thing to do is avoid having a sitemap and make damn sure that Google and any other search engine can properly spider your site using the plain old standard web pages everyone else sees. By the time you have done that, and are getting spidered nice and thoroughly so Google can see that your own site links to these pages, and would be willing to crawl the links -- uh, why do we need a sitemap, again? The sitemap can be actively harmful, because it distracts you from ensuring that search engine spiders are able to successfully crawl your whole site. &quot;Oh, it doesn't matter if the crawler can see it, we'll just slap those links in the sitemap!&quot; Reality is quite the opposite in our experience. That seems more than a little ironic considering sitemaps were intended for sites that have a very deep collection of links or complex UI that may be hard to spider. In our experience, the sitemap does not help, because if Google can't find the link on your site proper, it won't index it from the sitemap anyway. We've seen this proven time and time again with Stack Overflow questions. Am I wrong? Do sitemaps make sense, and we're somehow just using them incorrectly? How to show that $P(A\cup B) = P(A) + P(B) - P(A\cap B)$ Say we have a venn diagram with A on the left, intersection C in the middle and B on the right.   I want to show that $P(A\cup B) = P(A) + P(B)  - P(A\cap B)$  I know what it can be written as A+B+C, but a lot of the proofs  go from:  $P(A\cup B) = P(A) + P(B)  + P(C)$ to  $P(A) + P(B) = P(A\cup B)  + P(C) $  and then rearrange to  get the proof and get $P(A\cup B) =P(A) + P(B)-  P(C) $ . I just don't get how the left side of the inequality get go from $P(A\cup B)$  to $P(A) + P(B)$. Doesn't that only happen if we assume that they are disjoint. In this case, do we assume that they are disjoint? I know how to write the proof but just having a hard time actually understanding it. Provide an easily discoverable way to get the full URL to an answer , clicking &quot;link&quot; &quot;share&quot; for anwers yields a short (traceable) URL in the &quot;share a link to this answer&quot; dialog, such as †:  These short URLs show no clue about the linked question whatsoever. Also, when different people use a short URL for the very same post, then the user id suffix makes those be different URLs for a browser. Such links will then not be shown as visited‡. I know how to get URLs that have a proper slug. But as I see  pop up on these sites (where referrals ), I assume many others just don't realize full URLs would be better for use on these sites themselves? Or many don't want to do the little effort to get the full URL? So: can we please have an easy way to get the full URL as well, in a way that is easily found for those who don't know about the different links? (Currently for questions, clicking &quot;link&quot; has the same effect. But then one can also right-click the title, or take the URL from the location bar, to get the full human-readable URL. Once, Jeff .)  † The short links for answers are not (yet) [automatically converted][6] into a clickable question title either, unlike links such as `https://meta.stackexchange.com/questions/74274/privacy-leak-in-permalink#75963`, which renders as https://meta.stackexchange.com/questions/74274/privacy-leak-in-permalink#75963 But I guess that will change soon.  ‡ On Meta the CSS for posts doesn't indicate such difference anyway, which is a different issue.