What are the multidimensional versions of the median and what are their pros and cons? I confess this doesn't have a single answer, but I think it is a useful question to ask and will be a benefit to others as well.  How stable it is (i.e. how many samples one needs to get a reasonable estimate of it) is one potential, but not necessary, pro and con issue, i.e. if you know that the number of samples necessary grows exponentially with each increase in dimension making it useful in 10 dimensions but effectively useless in 200 dimensions, that would be useful to know. (I would kind of expect all of them have that, really, because there is so much "freedom" in 200 dimensions it just takes a bazillion points to nail the basic middle of a distribution down along that many directions).  Note: I found  after accepting an answer for this. I hadn't seen it before because I didn't realize there was both a multivariate-analysis and a multivariable tag. I am not sure why geometric median was an unpopular answer there (1 vote and near the bottom) but a popular answer here.
If so, what? If not, why not?  For a sample on the line, the median minimizes the total absolute deviation. It would seem natural to extend the definition to R2, etc., but I've never seen it. But then, I've been out in left field for a long time.
How do I back up AWS S3 and EBS to a non-Amazon provider? We've centered most of our operations on AWS, and love the ease of use there. However, every once in a while, the paranoid side of my brain wonders ?  Within the Amazon ecosystem, we have a pretty good backup plan: We keep most static data in S3. EBS volumes are snapshotted nightly. However, true paranoia would mean backing up to a provider outside the Amazon ecosystem. How do you handle doing this? I'm especially interested in backing up EBS snapshots and S3 contents. Bonus points for backing up RDS. What i did?   [root@mdfdevha1 ~]# Group_ID=`/opt/keycloak/bin/kcadm.sh get groups -r TEST`  [root@mdfdevha1 ~]# echo $Group_ID [ { "id" : "57c86153-11ba-4d19-aafb-9903ee00086b", "name" : "Admin_UserGroup", "path" : "/Admin_UserGroup", "subGroups" : [ ] } ] [root@mdfdevha1 ~]# SURE_USER_ID=`echo $Group_ID | cut -d : -f2 | awk -F\" '{print $2}'` [root@mdfdevha1 ~]# echo $SURE_USER_ID 57c86153-11ba-4d19-aafb-9903ee00086b   In this case i am able to get the id but my requirement little bit complex  I run below command   [root@mdfdevha1 ~]#  Group_ID=`/opt/keycloak/bin/kcadm.sh get groups -r My_Realm`   and then   [root@mdfdevha1 ~]# echo $Group_ID   Output was multiple record in JSON format  [ { "id" : "e27206c0-aeb6-43db-acda-c4ba43233071", "name" : "A1", "path" : "/A1", "subGroups" : [ ] },  { "id" : "89f3bd6a-33a9-4e02-9fe3-eae660c5a6cf", "name" : "Admin_UserGroup", "path" : "/Admin_UserGroup", "subGroups" : [ ] },  { "id" : "cdc2bce5-c3bb-4b88-bdaf-d87b8bb6c644", "name" : "Group104", "path" : "/Group104", "subGroups" : [ ] },  { "id" : "a0d749f2-ab6c-4c27-ad55-3357eaab9527", "name" : "Group105", "path" : "/Group105", "subGroups" : [ ] },  { "id" : "fbf99c34-d50d-408b-8d19-9713f9af3e3a", "name" : "Group106", "path" : "/Group106", "subGroups" : [ ] },  { "id" : "ebd8336f-4017-4fb1-8035-153ae1d9ba37", "name" : "Group201", "path" : "/Group201", "subGroups" : [ ] },  { "id" : "38f4aef7-caf0-4430-9e61-1ae7026e872f", "name" : "Group202", "path" : "/Group202", "subGroups" : [ ] },  { "id" : "436a0f4a-8b1b-4d7d-a014-fcec3513644e", "name" : "Group203", "path" : "/Group203", "subGroups" : [ ] },  { "id" : "41962c5f-e7e9-4748-b81f-e3f1880b78de", "name" : "Sure_Groups", "path" : "/Sure_Groups", "subGroups" : []}]   Now from the above output i want to get the ID where name = Admin_UserGroup.  How can this will achieve ? Possible Duplicate:          I was wondering if there's any good reason to still use blob fields in a database. A couple of years ago I worked with a DB with a bunch of images in it, the DB was very slow and I couldn't see any good reason to keep the images inside the DB, so I got the images out and stored the filenames instead.  Was this a smart move? What would you do in my place? Convergence of $\sum_{n=1}^\infty{\left(\sqrt[n]{n}-1\right)}$ From Wikipedia: Fermi was known for his ability to make good approximate calculations with little or no actual data, hence the name. One example is his estimate of the strength of the atomic bomb detonated at the Trinity test, based on the distance travelled by pieces of paper dropped from his hand during the blast. Fermi's estimate of 10 kilotons of TNT was remarkably close to the now-accepted value of around 20 kilotons, a difference of less than one order of magnitude.  I have not been able to find any references explaining how he made this calculation. Please provide a reference or an example calculation.  See also: I took several statistics courses in college but I found that my education was very theory driven.  I was wondering if any of you had a text in Applied Statistics (at the graduate level) that you recommend or have had good experience with. I am trying to retrieve list items using date range based on date column. It implicit both 'Fromdate' and 'Todate'.My CAML query is also querying on two other conditions as well. I am using the below query but it is not retrieving the data.when I remove the date range from query data is retrieved fine. But i want date range as well in my query how would i do this. Little help would work for me.   camlQuery.set_viewXml('&lt;View&gt;&lt;Query&gt;&lt;Where&gt;&lt;And&gt;&lt;And&gt;&lt;Neq&gt;&lt;FieldRef Name="ID" /&gt;&lt;Value Type="Number"&gt;0&lt;/Value&gt;&lt;/Neq&gt;&lt;Eq&gt;&lt;FieldRef Name="_ModerationStatus" /&gt;&lt;Value Type="ModStat"&gt;0&lt;/Value&gt;&lt;/Eq&gt;&lt;Geq&gt;&lt;FieldRef Name="Created" /&gt;&lt;Value Type="DateTime"&gt;' + fromDate + '&lt;/Value&gt;&lt;/Geq&gt;&lt;Leq&gt;&lt;FieldRef Name="Created" /&gt;&lt;Value Type="DateTime"&gt;' + toDate + '&lt;/Value&gt;&lt;/Leq&gt;&lt;/And&gt;&lt;/And&gt;&lt;/Where&gt;&lt;OrderBy&gt;&lt;FieldRef Name="_ModerationStatus" Ascending="True" /&gt;&lt;/OrderBy&gt;&lt;/Query&gt;&lt;/View&gt;'); Is there way to move one vertex and make another move with it proportionally? I'll try to explain in this gif. I am doing this manually in 2 steps - rotate, scale. And I select all vertexes. Is there instrument rotate them in one step or can I move one and make other move too? Why are the holodecks on Voyager in use if they have energy issues? I'm watching the first two seasons of Voyager and various episodes have commentary on having energy limitations -- but we constantly see crew using extremely complicated holodeck simulations. Why would they allow use of the holodeck if they need to conserve energy? Why did Dumbledore tell Harry there were 6 Horcruxes when he already knew Harry was a horcrux? Harry: "He made seven Horcruxes?"   Dumbledore: "...Not seven Horcruxes: six. The seventh part of his soul, however maimed, resides inside his regenerated body..." (HP6, US Hardback, page 503).    I would think that Dumbledore had already known that there were 6 horcruxes:    the diary  Gaunt's ring  Salazar's locket Helga Hufflepuff's cup Nagini (the whole essence divided thing)   Now those are the five that he was sure of. He knew that when Riddle came to Hogwarts to ask for the DADA position, he was really there so he could hide a horcrux. (But he never got a chance to tell Harry that, right?) Did Dumbledore know of the diadem? Or did he just think Riddle wanted to hide the cup?   Did Dumbledore say there were 6 and not 7 because he didn't know about the diadem but did know about Harry being a horcrux? Or did he say there were 6 to ensure Harry didn't guess he was a horcrux? Sorry if this makes no sense.  I know that in the end there were 7 horcruxes and an 8th part of Voldemort's soul right? How to connect to Android through SSH over 3G/4G public IP? Is it possible to make a sequence of renders and give the user the option to cancel the process through the UI at any given time? How to know when to change a chain? A bike shop employee used a tool he said would check the wear on the chain, and said that it should be changed.   He said it took a measurement that meant the chain had expanded, but it is still hard for me understand why I should change the chain.   He said that the reason was that the expanded chain links will cause the chain rings to wear down.   That is one argument and I have no experience with it, to know if it is true.   But are there more reasons? How do I know when the chain should be changed?   My first thought is to use it until it breaks, but it probably is not the wisest option. Can there be more than one power series expansion for a function. I guess the answer is NO, for polynomials.  I know that there are more than one series expansion for every function.  But I am talking about power series here.  All Ideas are appreciated Does Stack Exchange have an Economics section? As far as I know, those are the only two.  They should be pronounced Soogher and Soor, shouldn't they?  I looked them up on Dictionary.com, and their etymologies reveal no trace of an SH, except where the listing for sugar had:     Middle English sugre, sucre (noun) &lt; Middle French sucre  &lt; Medieval Latin succārum  &lt; Italian zucchero  &lt; Arabic sukkar;  obscurely akin to Persian shakar, Greek sákcharon   I see an obscure kinship to shakar, but the word morphed so many times since then that the SH disappeared pretty much completely.  And sure is even worse, with no sign of SH:     Middle English sur ( e ) &lt; Middle French sur, Old French seur  &lt; Latin sēcūrus   Why are these the only two like this? Rendered image is just grey Why do I get different outputs in case of sh and bash? Nginx rewite rules 403 error I am having trouble with converting .htaccess files to nginx. I have 3 .htaccess files. The first .htaccess file is located in the document root and is as follows:  Options +FollowSymLinks RewriteEngine On RewriteRule ^img-(.*)\.html img.php?id=$1 [L] RewriteRule ^slide-(.*)\.html slider.php?id=$1 [L] RewriteRule ^page-(.*)\.html page.php?name=$1 [L] RewriteRule ^contact\.html$ contact.php [QSA,L,NC]   The second .htaccess file is located in a folder called upload:  RewriteEngine On RewriteCond %{HTTP_REFERER} !^http://(.+\.)?foo\.com/ [NC] RewriteCond %{HTTP_REFERER} !^$ RewriteRule .*\.(jpe?g|gif|bmp|png)$ nohotlink.gif [L] &lt;Files ~ "\.(php|sql|php3|php4|phtml|pl|py|jsp|asp|htm|shtml|sh|cgi)$"&gt;   order allow,deny   deny from all &lt;/Files&gt;   And the third and final .htaccess file is found in a subdirectory of the upload folder named "small":  RewriteEngine Off   Now I have created a folder in /etc/nginx called includes and made 3 seperate .access files with these rewrite rules:  For the first .htaccess file located in the document root directory I have created an file in /etc/nginx/includes called root.access. In this file I have:  # nginx configuration   location /img {  rewrite ^/img-(.*)\.html /img.php?id=$1 break;  }  location /slide {      rewrite ^/slide-(.*)\.html /slider.php?id=$1 break;  }  location /page {      rewrite ^/page-(.*)\.html /page.php?name=$1 break;  }  location /contact {      rewrite ^/contact\.html$ /contact.php break;  }   For the second file located in the "upload" folder I have crated a file in /etc/nginx/includes called upload.access. This file contains the following:  # nginx configuration   location /upload {  if ($http_referer !~ "^http://(.+\.)?foo\.com/"){  rewrite .*\.(jpe?g|gif|bmp|png)$ /nohotlink.gif break;  }  }  location ~ \.(php|sql|php3|php4|phtml|pl|py|jsp|asp|htm|shtml|sh|cgi)$ {  deny all;  }   And for the third and final file I have created a file in /etc/nginx/includes names small.access. The contents of this file are as follows:  # nginx configuration   location /upload/small {  }   In the server block configuration file I have:   location / {               try_files $uri $uri/ /index.php;               include /etc/nginx/includes/root.access;      }   location /upload {               include /etc/nginx/includes/upload.access;      }   location /upload/small {               include /etc/nginx/includes/small.access;      }   Now with this configuration when trying the site I receive 403 errors. Nginx error log reports:  [error] 18156#0: *7 access forbidden by rule, client: 111.**.**.**, server: foo.com, request: "POST /upload.php HTTP/1.1", host: "foo.com", referrer: "http://foo.com/"   Now under apache everything works no problems. But I can not see why I am getting 403 errors. I am also worried that the rewrite rules as I have stated them, beyond the 403 error will not function properly at all. Can anyone help me with this? I can not see what is wrong here. Make mod_wsgi use python2.7.2 instead of python2.6? i am running Ubuntu 10.04.1 LTS  and it came pre-packed with python2.6 but i need to replace it with python2.7.2.   (The reason is simple, 2.7 has a lot of features backported from 3 )  i had installed python2.7.2 using  ./configure make make altinstall   the altinstall option installed it, without touching the system default version, to /usr/local/lib/python2.7 and placed the interpreter in /usr/local/bin/python2.7  Then to help mod_wsgi find python2.7 i added the following to /etc/apache2/sites-available/wsgisite  WSGIPythonHome /usr/local   i start apache and run a test wsgi app BUT i am greeted by python 2.6.5  and not Python2.7  Later i replaced the default python simlink to point to python 2.7  ln -f /usr/local/bin/python2.7 /usr/bin/python   Now typing 'python' on the console opens python2.7 but somehow mod_wsgi still picks up python2.6  Next i tried,  PATH=/usr/local/bin:$PATH export PATH   then do a quick restart apache, but yet again its python2.6 !!    Here is my $PATH  /usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games   contents of /etc/apache2/sites-available/wsgisite  WSGIPythonHome /usr/local   &lt;VirtualHost *:80&gt;      ServerName wsgitest.local     DocumentRoot /home/wwwhost/pydocs/wsgi     &lt;Directory /home/wwwhost/pydocs/wsgi&gt;         Order allow,deny         Allow from all     &lt;/Directory&gt;      WSGIScriptAlias / /home/wwwhost/pydocs/wsgi/app.wsgi  &lt;/VirtualHost&gt;   app.wsgi  import sys  def application(environ, start_response):     status = '200 OK'     output = sys.version      response_headers = [('Content-type', 'text/plain'),                         ('Content-Length', str(len(output)))]     start_response(status, response_headers)      return [output]   Apache error.log  'import site' failed; use -v for traceback [Sun Jun 19 00:27:21 2011] [info] mod_wsgi (pid=23235): Initializing Python. [Sun Jun 19 00:27:21 2011] [notice] Apache/2.2.14 (Ubuntu) mod_wsgi/2.8 Python/2.6.5 configured -- resuming normal operations [Sun Jun 19 00:27:21 2011] [info] Server built: Nov 18 2010 21:20:56 [Sun Jun 19 00:27:21 2011] [info] mod_wsgi (pid=23238): Attach interpreter ''. [Sun Jun 19 00:27:21 2011] [info] mod_wsgi (pid=23239): Attach interpreter ''. [Sun Jun 19 00:27:31 2011] [info] mod_wsgi (pid=23238): Create interpreter 'wsgitest.local|'. [Sun Jun 19 00:27:31 2011] [info] [client 192.168.1.205] mod_wsgi (pid=23238, process='', application='wsgitest.local|'): Loading WSGI script '/home/wwwhost/pydocs/$ [Sun Jun 19 00:27:50 2011] [info] mod_wsgi (pid=23239): Create interpreter 'wsgitest.local|'.   Has anybody ever managed to make mod_wsgi run on a non-system default version of python ?