How do I get the co-ordinates of the spheres from the output of this code?
How can I extract the points from a ListSurfacePlot3D?
If $n\times n$ matrix $A$ has eigenvalues $1,-1$ and $n\times n$ matrix $B$ also has eigenvalues $1,-1$, can I then say something about eigenvalues of $AB$ and $BA$? Why are Perl 5's function prototypes bad? What is the most effective way for float and double comparison? Looking for an intuitive explanation why the row rank is equal to the column rank for a matrix I am looking for an intuitive explanation as to why/how row rank of a matrix = column rank. I've read the proof at  and I understand the proof, but I don't "get it". Can someone help me out with this ?   I find it hard to wrap my head around the idea of how the column space and the row space is related at a fundamental level. Can I take a sex-toy on plane through UAE? I will be traveling from Australia to Austria, transferring in Abu Dhabi. Is it alright for me to bring a vibrator in the check-in luggage, or are there laws against that?  It is approximately 17cm long. Are there any precautions to take? How to read "service --status-all" results I need to identify the currently running services but I can't figure out the results of running service --status-all, I mean what does ?, - and + mean ?  $ service --status-all  [ + ]  acpid  [ + ]  anacron  [ + ]  apparmor  [ ? ]  apport  [ ? ]  atieventsd  [ + ]  avahi-daemon  [ ? ]  binfmt-support  [ + ]  bluetooth  [ - ]  brltty  [ + ]  console-font  [ + ]  console-setup  [ + ]  cron  [ + ]  cups  [ + ]  cups-browsed  [ - ]  dbus  [ ? ]  dns-clean  [ + ]  friendly-recovery  [ - ]  grub-common  [ ? ]  irqbalance  [ - ]  kerneloops  [ ? ]  killprocs  [ + ]  kmod  [ ? ]  lightdm  [ - ]  lm-sensors  [ ? ]  mysql  [ ? ]  networking  [ ? ]  ondemand  [ ? ]  pppd-dns  [ - ]  procps  [ - ]  pulseaudio  [ ? ]  rc.local  [ + ]  resolvconf  [ + ]  rfkill-restore  [ + ]  rfkill-store  [ - ]  rsync  [ + ]  rsyslog  [ + ]  saned  [ ? ]  sendsigs  [ + ]  setvtrgb  [ ? ]  speech-dispatcher  [ - ]  sudo  [ + ]  timidity  [ + ]  udev  [ ? ]  umountfs  [ ? ]  umountnfs.sh  [ ? ]  umountroot  [ - ]  unattended-upgrades  [ - ]  urandom  [ + ]  virtualbox  [ - ]  x11-common   And would running this command with sudo make any difference ? I tried it and in my case it didn't make any difference, but may it differ in other setups ? Fedora 25 and disabling whatever is listening on port 111 I've got a Fedora 25 x86_64 stand alone workstation. Something is listening on port 111 (identified with an nmap scan):  $ sudo lsof -i :111 COMMAND PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME systemd   1 root   36u  IPv4  15170      0t0  TCP *:sunrpc (LISTEN) systemd   1 root   37u  IPv4  15171      0t0  UDP *:sunrpc systemd   1 root   38u  IPv6  15172      0t0  TCP *:sunrpc (LISTEN) systemd   1 root   39u  IPv6  15173      0t0  UDP *:sunrpc   I disabled the Sun gear on the port with the following commands:  $ sudo systemctl disable rpcbind $ sudo systemctl disable sunrpc Failed to disable unit: No such file or directory   After reboot the port is still open.  It appears something other than Sun gear wants to listen on port 111. Or maybe systemd is not respecting my wishes to disable the unused service. Or maybe something else...  How do I determine what is trying to listen on the port, and how do I disable it?    From below:  $ sudo systemctl -a | grep -E "rpc|port"   var-lib-nfs-rpc_pipefs.mount          loaded    active   mounted   RPC Pipe File System   abrtd.service                         loaded    active   running   ABRT Automated Bug Reporting Tool   auth-rpcgss-module.service            loaded    inactive dead      Kernel Module supporting RPCSEC_GSS   fedora-import-state.service           loaded    active   exited    Import network configuration from initramfs   fedora-readonly.service               loaded    active   exited    Configure read-only root support   rpc-gssd.service                      loaded    inactive dead      RPC security service for NFS client and server   rpc-statd-notify.service              loaded    inactive dead      Notify NFS peers of a restart   rpc-statd.service                     loaded    inactive dead      NFS status monitor for NFSv2/3 locking. ● rpc-svcgssd.service                   not-found inactive dead      rpc-svcgssd.service   rpcbind.service                       loaded    inactive dead      RPC Bind   rpcbind.socket                        loaded    active   listening RPCbind Server Activation Socket   rpc_pipefs.target                     loaded    active   active    rpc_pipefs.target   rpcbind.target                        loaded    active   active    RPC Port Mapper How is The Wall bypassed? In the first series of the TV show several things apparently bypass  to reach Winterfell:   The Night's Watch member  captured near Winterfell and executed by Ned. The Direwolf &amp; her pups found immediately after the execution  and the other Wildlings travelling with her   If The Wall is approximately the same along its length it would presumably be impassible. Is the only option for them to go around the western end (since it stops at the Shadow Tower)? Is this clarified in the book? Are other methods mentioned in subsequent books? Getting a System.Type from type's partial name I want to get a System.Type given only the type name in a string.  For instance, if I have an object:  MyClass abc = new MyClass();   I can then say:  System.Type type = abc.GetType();   But what if all I have is:  string className = "MyClass"; Me and my friends want to listen to music together. Two of us have Bluetooth Headphones (Beats Solo2 Wireless, Beats Studio Wireless) and one has a wired headset. Is there any way to use all three of these together? I want to show that if a real orthogonal matrix $A$ has determinant $-1$ then $\lambda=-1$ must be an eigenvalue of $A$.  I have proven this in a long-winded way and I was wondering if these is a quick way of seeing it. How to get dialog box input directed to a variable? I have been teaching myself bash scripting and have run into an issue. I have written a script to take input from the user, using the 'read' command, and make that input a variable to use later in the script. The script works, but....  I would like to be able to get it setup using 'dialog'. I found out that  'dialog --inputbox' will direct the output to 'stderr' and in order to get that input as a variable you have to direct it to a file and then retrieve it. The code I found to explain this is:  #!/bin/bash dialog --inputbox \  "What is your username?" 0 0 2&gt; /tmp/inputbox.tmp.$$  retval=$?  input=`cat /tmp/inputbox.tmp.$$`  rm -f /tmp/inputbox.tmp.$$  case $retval in 0)  echo "Your username is '$input'";; 1)  echo "Cancel pressed.";;  esac   I see that it is sending the sdterr to the /tmp/inputbox.tmp.$$ with 2>, but the output file looks like 'inputbox.tmp.21661'. When I try and cat the file it gives me an error. So I am still unable to get the user input from the --inputbox as a variable.   Example Script:   echo "  What app would you like to remove? "  read dead_app  sudo apt-get remove --purge $dead_app   So as you can see it is a basic script. Is it even possible to get the variable as a word from dialog --inputbox? What is Renly's basis for removing Joffrey? Related question:   I get that he considers himself a better king than Stannis, but why isn't he ?  Did Renly know about Joffrey being illegitimate? I always thought he didn't and was distrustful that Cersei would accept Ned as Regent.  I think in both the books and the series, Renly finds out Joffrey is illegitimate from Stannis' letters, but rewatching that clips makes me think Renly was with Ned, Varys and LF in the plan to arrest Joffrey and Cersei.  [looks up something]  Oh also . So Renly did know? Learning Insertion Sort in Ruby I have just started the MIT Introduction to Algorithms course through the material posted online. Along with the course I have also decided to learn/enhance my Ruby skills by coding the algorithms in it.   I am on the first algorithm given, which is Insertion sort, and I have the following code typed up but I am getting this error when I run it:     insertionsort.rb:5:in `>': comparison of Fixnum with nil failed (ArgumentError)   def  insertionsort(num) for j in 2..num.length     key = num[j]     i = j - 1     while i &gt; 0 and num[i] &gt; key         num[i+1] = num[i]         i = i - 1     end     num[i+1] = key end  puts num end  numbers = [23,34,46,87,12,1,66]  insertionsort(numbers)   I'm sure it is a fairly basic problem but I just can't grasp what it is at the moment. Any  help or tips would be very much appreciated. If $f'$ is differentiable at $a$ then $f'$ is continuous at $(a-\delta,a+\delta)$ QGIS query syntax differs between attribute table and feature filter Using QGIS 2.16.2, I can successfully select records from a shapefile attribute table using the following expression:  left("start_time", 10) = '2015-08-01'   Please note that start_time is a string field.  However, when I copy and paste the same expression into the shapefile's Layer Properties>General>feature filter>Query Builder I get the following error:    I would expect that the same expression would work everywhere in QGIS.  What am I doing wrong? It worked with the pre-installed Ubuntu, but after re-installing Ubuntu dual-boot with Windows 8.1, the WiFi is not working.  Is there a driver for this adapter that will work on Ubuntu 12.04? How do I restore /usr/bin/env after overwriting it with start-tor-browser file I was installing Tor and wanted to access it directly from the terminal, so I was trying to copy start-tor-browser to /usr/bin. But by mistake, I have replaced the /usr/bin/env file with the start-tor-browser file. What should I do now?? System.FinalException: Record is read-only: Trigger.updateCompetitors: line 24 According to two questions  and  asked on this site earlier there exists a nice relation:  $$\frac1{n!} \left(\int_{0}^t\mathrm dt \; f(t)\right)^n = \int_{0}^t\mathrm dt_1 \int_{0}^{t_1}\mathrm dt_2 \cdots \int_{0}^{t_{n-1}}\mathrm dt_n\; f(t_1)\,f(t_2) \ldots f(t_n). $$  Unfrotunatly I am more interested in integrals of the form  $$\int_{0}^t\mathrm dt_1 \int_{0}^{t_1}\mathrm dt_2 \cdots \int_{0}^{t_{n-1}}\mathrm dt_n\; f(t_n). $$  Can it be somehow brought to an unary integral?  All I have figured out by now is that  $$\int_{0}^t\mathrm dt_1 \int_{0}^{t_1}\mathrm dt_2 \cdots \int_{0}^{t_{n-1}}\mathrm dt_n\; t_n^m = \frac{m!}{(m+n)!} t^{m+n} .$$