Beautiful random graphs
Random plot based on a specific random seed
DKIM sign outgoing mail from any domain (with Postfix and Ubuntu) I got DKIM setup on my mail server (postfix and ubuntu) so it signs outgoing emails.  I used these instructions:   However, I need it to sign emails from any domain (in the From address) and not just my own.  I'm building an email newsletter service and clients will be sending their own email through the server.  First I set "Domain *" in /etc/dkim-filter.conf.  This got it to include the DKIM headers in all outgoing emails, no matter what the domain.  However, the verification check fails on gmail because it is checking the domain in the from address, and not my domain (and dns record).  Does anyone know how to do this? Show that  $$t(n) = 1 + \sum_{ j=0}^{n-1} t(j)$$  is the same as  $$t(n) = 2^n$$  Initial condition $t(0) = 1$ A 398MB directory was only compressed to 393MB using 7Z and Normal ZIP compression. Is this normal? If so, why do people continue to use ZIP on Windows? Are mirror lenses good for wildlife photography in daylight? I've recently seen these Rokinon/Opteka mirror lens with whooping focal length (like 500mm, 600mm, 800mm, 1000mm) at a cheap price. And I have seen some of their same pictures in Flickr and vendor sites. But the only thing is that they usually starts from smaller aperture (f/5.6 and upwards)   Now what I was wondering, as they are cheap with quite good IQ - are they good for any bird photography or wild life photography in proper daylight? How to get pixel data from a UIImage (Cocoa Touch) or CGImage (Core Graphics)? pygame installation issue in mac os change thickness median line geom_boxplot() Replace strings in a file based on a list of strings and a list of corresponding replacements Using a foreign driver's license in California when staying with a J-1 visa I'm planning to attend a Californian university as a visiting scholar (not paid by the university) on a J-1 visa, for a total of four weeks; a colleague of mine will do the same, but for 12 weeks. I've been told (personally, ie. no citable sources) that, if you're staying on a J-1, you're effectively a California resident for the time you're there, and, therefore, need a Californian driver's license.  I've read up on this and found  that states:     If you are a visitor in California over 18 and have a valid driver   license from your home state or country, you may drive in this state   without getting a California driver license as long as your home state   license remains valid.      If you become a California resident, you must get a California driver   license within 10 days. Residency is established by voting in a   California election, paying resident tuition, filing for a homeowner's   property tax exemption, or any other privilege or benefit not   ordinarily extended to nonresidents.   I'm not planning to vote in any elections, nor will I own a home there, but I'm not sure what would constitute "privileges or benefits not ordinarily extended to nonresidents".  Do we need to get driver's licenses in California, or can we use our foreign licenses? How about day trips to Arizona or Nevada?  Note: this seems to be related to , but my question is specifically about staying there on a J-1. Changing subject and verb positions in statements and questions We always change subject and verb positions in whenever we want to ask a question such as "What is your name?". But when it comes to statements like the following, which form is correct?        I don't understand what are you talking about.   I don't understand what you are talking about.      Another example        Do you know what time is it?   Do you know what time it is?      Another example        Do you care how do I feel about this?   Do you care how I feel about this? Using getopts to process long and short command line options Why does parameter expansion with spaces without quotes work inside double brackets "[[" but not inside single brackets "["? I'm confused with using single or double brackets. Look at this code:  dir="/home/mazimi/VirtualBox VMs"  if [[ -d ${dir} ]]; then     echo "yep" fi   It works perfectly although the string contains a space. But when I change it to single bracket:  dir="/home/mazimi/VirtualBox VMs"  if [ -d ${dir} ]; then     echo "yep" fi   It says:  ./script.sh: line 5: [: /home/mazimi/VirtualBox: binary operator expected   When I change it to:  dir="/home/mazimi/VirtualBox VMs"  if [ -d "${dir}" ]; then     echo "yep" fi   It works fine. Can someone explain what is happening? When should I assign double quotes around variables like "${var}" to prevent problems caused by spaces? Relative pronouns "where" and "when": where can they be omitted? I know the "omitting-rules" regarding the relative pronouns who/which/that and whose. How does it work with where and when? In the first sentence I cannot omit where but I can easily omit when in the second sentence. What is the rule?   I saw John in the shop where you bought your brown T-shirt. I met Laura on the day (when) I missed the train to Barcelona. Can sum of a rational number and its reciprocal be an integer? Can sum of a rational number and its reciprocal be an integer?   My brother asked me this question and I was unable to answer it.   The only trivial solutions which I could think of are $1$ and $-1$.  As to what I tried, I am afraid not much. I have never tried to solve such a question, and if someone could point me in the right direction, maybe I could complete it on my own.  Please don't misunderstand my question.   I am looking for a rational number $r$ where $r + \frac{1}{r}$ is an integer. "Open in Terminal" in Ubuntu 18.04 This option seems to have gone away after upgrading from Ubuntu 16.04. I tried installing nautilus-open-terminal but it is unable to locate the package for 18.04. Also trying to install nautilus-actions gives:  Package nautilus-actions is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source     How to fix this? Show that $\lim _{r \to 0} \|T_rf−f\|_{L_p} =0.$ Is there a way in Adobe Creative Suite to "share palettes/swatches" across programs? I use a mixture of InDesign, Photoshop and Illustrator to produce the vast amount of printed media I design at my current position and I find myself faced with copy/pasting color values from one program to another almost all the time, I have tried to find a quicker way but have been unsuccessful. I use a program called  to copy and store my most used colors, but still, it's not the same as being able to select it from the swatches palette in Adobe CS.  So the main meat of the question is:   Can I share my colors/swatches between InDesign, Photoshop and Illustrator and if so, how? What is the origin of BrEng ‘bird’ meaning “young woman”? Bird:         (Brit.) a girl or young woman, esp one's girlfriend ()      According to  bird:         "maiden, young girl," c.1300, confused with   (q.v.), but felt by later writers as a figurative use of  (n.1). Modern slang meaning "young woman" is from 1915, and probably arose independently of the older word.      also :         , bird was used for ‘girl’, but this was probably owing to confusion with another similar middle English word, burde, which also meant ‘young woman’. The usage crops up from time to time in later centuries, clearly as an independent metaphorical application, but there does not really seem to be an unbroken chain of occurrences leading up to the sudden explosion in the use of bird for ‘young woman’ in the 20th century.   (www.dictionarycentral.com)      Modern usage of bird meaning girl appears to be unrelated to the old Middle Ages meaning. Etymonline dates it back precisely to 1915.    What is the modern origin of bird meaning young woman?  In what context did they start to use it at the beginning of the 20th century? How to get the valid URL of a Link field from within a Twig template? I have a Link field named field_my_link (machine name).  Within a Twig template I can get the link's URL value with this:  {{ node.field_my_link.uri }}   If inside the Link's URL there is an external URL, e.g. http://example.com it works good.  But, if inside the Link's URL there is stored an internal URL, e.g. "/node/11", I get a value like this:  "internal:/node/11"   with the "internal:" prefix.  How can I get the valid URL?  For example, if the link's URL is "http://example.com" I want "http://example.com" (this already works), if the link's URL is "/node/11" I want the relative URL "/node/11", if the link's URL is "&lt;front&gt;" I want the URL "/", etc.    EDIT  I can get the value I want within a PHP preprocess function, using this:  $url = $variables['node']-&gt;get('field_my_link')-&gt;first()-&gt;getUrl();   How can I access the same value within the Twig template?  I know I can do this within the preprocess function:  $variables['my_url'] = $url;   Then access the url within Twig using {{ my_url }}, but I would avoid to write a preprocess function each time I have a link field. Modelling with more variables than data points I'm fairly new to Machine Learning/Modelling and I'd like some background to this problem. I have a dataset where the number of observations is $n&lt;200$ however the number of variables is $p\sim 8000$. Firstly does it even make sense to consider building a model on a dataset like this or should one consider a variable selection technique to start with such as ridge regression or Lasso? I've read that this situation can lead to over-fitting. Is that the case for all ML techniques or do some techniques handle this better than others? Without too much maths a simple explanation on why the maths start to breakdown for $p&gt;n$ would be appreciated.