I want to plot an ellipse whose size would be defined somewhere above:  \begin{tikzpicture}   \def\semix{0.1}   \def\semiy{0.2}   \draw (0,0) ellipse (\semix and \semiy); \end{tikzpicture}   which gives the following error  ! Package PGF Math Error: Unknown operator `a' or `an' (in '0.1and 0.2').  See the PGF Math package documentation for explanation. Type  H &lt;return&gt;  for immediate help.  ...                                                l.8 ...\draw (\x+1,\y) ellipse (\semix and \semiy)                                                   ; This error message was generated by an \errmessage command, so I can't give any explicit help. Pretend that you're Hercule Poirot: Examine all clues, and deduce the truth by order and method.   ! Package PGF Math Error: Unknown operator `a' or `an' (in '0.1and 0.2').  See the PGF Math package documentation for explanation. Type  H &lt;return&gt;  for immediate help.  ...                                                l.8 ...\draw (\x+1,\y) ellipse (\semix and \semiy)                                                   ; (That was another \errmessage.)   it seems that \semix consumes the space after it. However adding a backslash after it doesn't solve the problem. Actually, the number of errors rises to 11.  Is there any workaround?
I want to use some constants, height and width, when creating an ellipse but it won't work with \newcommand. Here is a minimal example:  \documentclass[12pt, a4paper]{article}  \usepackage{amsthm, tikz} \usetikzlibrary{arrows, shapes, trees, positioning} \begin{document}  \begin{figure} \centering \begin{tikzpicture}       \newcommand*{\width}{2}%     \newcommand*{\height}{0.5*\width}%      \draw[fill=gray!40] (0, 0) ellipse (\width and \height); \node (Y) at (0,0) {\(Y\)};      \end{tikzpicture} \end{figure}  \end{document}    I get the following error:  error: line 14:  Package PGF Math Error: Unknown operator `a' or `an' (in '2and 0.5*2'). ...ay!40] (0,0) ellipse (\width and \height)
The [ifs] tag is used for 2 separate things I think  might correspond to IBM's  according to this .   But currently out of the 27 question tagged with , most of it have to do with the 's "Internal Field Separator".  What should be done here?   create a new tag for "Internal Field Separator" e.g. , and keep the IBM's under ? create a new tag for "Integrated File System" e.g. , and keep the other one under ? just remove the  tag from the  questions? This is about a step in a derivation of the expression for the relativistic Doppler effect.  Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is emitted at frequency $f_s$ and wavelength $\lambda_s$. The frequency $f_0$ and wavelength $\lambda_0$ received by the observer will be different.  Some textbooks now argue that the wavelength received by the observer is given by $\lambda_0=(c+u)T_0$, where $T_0$ is the time period of the wave in the observers frame. The argument given is that the successive "crests" will be an extra distance $uT_0$ apart due to movement of the source. Upon relativistically transforming the time period in the source frame to the observer frame, the correct result $f_0=f_s\sqrt{\frac{c-u}{c+u}}$ is obtained.  But the argument for the wavelength seems reminiscent of the classical Doppler effect for sound. Is it really applicable here through this argument? And is there a way to show the same result for $\lambda_0$ mathematically? Paucity of words for relationships Please refer the following questions asked elsewhere on this site:       I am a native Hindi speaker; Hindi has a plethora of terms referring to relationships. To take a trivial example, the term uncle may refer to father's elder brother, father's younger brother, mother's brothers, father's sister's husband, mother's sister's husband, all of which have specific addresses in Hindi.  I discussed the same with one of my teachers. She had the opinion that the development of language mirrors the cultural moorings of the society that uses the language. Now, since all of the above relationships have distinct status and reverence in the Hindi speaking society, that calls for different addresses. That may well not be the case in English speaking societies.  Is that correct? What other linguistic reasons may account for such a dearth of vocabulary in English in this area? Real definition of "countable set" After the therapy, eight children (43%) became able to crawl/move on their back.   Or should I use "on their backs"?   Singular because each child only has one back, or plural because we're dealing with eight backs? "Deleted by {owner}" vs "Deleted by owner" in self deleted answers Does anyone know if there is an API to get the current monitor state (on or off) in Windows (XP/Vista/2000/2003)?  All of my searches seem to indicate there is no real way of doing this.    tries to use  which according to Microsoft's docs does not work for display devices.   In Vista I can listen to  but I do not seem to get events when the monitor is turned off manually.   In XP I can hook into WM_SYSCOMMAND SC_MONITORPOWER, looking for status 2. This only works for situations where the system triggers the power off.   The WMI Win32_DesktopMonitor class does not seem to help out as well.   Edit: Here is  on comp.os.ms-windows.programmer.win32 indicating there is no reliable way of doing this.   Anyone else have any other ideas? Pre-1972 sci-fi short story or novel: alien(?) tunnel where people try new moves and get destroyed if they're not the correct ones so i change my MAC address with macchanger -A wlp68s0b1 at boot with crontab, here is what happens when i disconnect and reconnect :  while connecting after boot :  rahman@debian:~$ macchanger -s wlp68s0b1 Current MAC:   00:22:31:c6:38:45 (SMT&amp;C Co., Ltd.) Permanent MAC: 00:00:00:00:00:00 (FAKE CORPORATION)   after disconnecting :  rahman@debian:~$ macchanger -s wlp68s0b1 Current MAC:   16:7b:e7:3c:d3:cd (unknown) Permanent MAC: 00:00:00:00:00:00 (FAKE CORPORATION)   after reconnecting :  rahman@debian:~$ macchanger -s wlp68s0b1 Current MAC:   00:00:00:00:00:00 (FAKE CORPORATION) Permanent MAC: 00:00:00:00:00:00 (FAKE CORPORATION)   and so on, and with every disconnect i get a different random MAC address which fades on reconnecting giving me my real MAC address , what causes that and how to stop it ?  some outputs :  rahman@debian:~$ lspci -nn |grep 14e4 44:00.0 Network controller [0280]: Broadcom Limited BCM4313 802.11bgn Wireless Network Adapter [14e4:4727] (rev 01) rahman@debian:~$ uname -a Linux debian 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2+deb9u5 (2017-09-19) x86_64 GNU/Linux rahman@debian:~$ sudo ifconfig  enp0s25: flags=4099&lt;UP,BROADCAST,MULTICAST&gt;  mtu 1500         ether 00:24:c0:7b:a8:8b  txqueuelen 1000  (Ethernet)         RX packets 0  bytes 0 (0.0 B)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 0  bytes 0 (0.0 B)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0         device interrupt 20  memory 0xd4800000-d4820000    enp0s25:avahi: flags=4099&lt;UP,BROADCAST,MULTICAST&gt;  mtu 1500         inet 169.254.9.109  netmask 255.255.0.0  broadcast 169.254.255.255         ether 00:24:c0:7b:a8:8b  txqueuelen 1000  (Ethernet)         device interrupt 20  memory 0xd4800000-d4820000    lo: flags=73&lt;UP,LOOPBACK,RUNNING&gt;  mtu 65536         inet 127.0.0.1  netmask 255.0.0.0         inet6 ::1  prefixlen 128  scopeid 0x10&lt;host&gt;         loop  txqueuelen 1  (Local Loopback)         RX packets 9436  bytes 6584515 (6.2 MiB)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 9436  bytes 6584515 (6.2 MiB)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  wlp68s0b1: flags=4163&lt;UP,BROADCAST,RUNNING,MULTICAST&gt;  mtu 1500         inet 192.168.1.5  netmask 255.255.255.0  broadcast 192.168.1.255         inet6 fe80::6711:9875:eb78:24fc  prefixlen 64  scopeid 0x20&lt;link&gt;         inet6 fd9c:c172:b03b:ce00:f1e0:695e:7da0:91a  prefixlen 64  scopeid 0x0&lt;global&gt;         ether 00:00:00:00:00:00  txqueuelen 1000  (Ethernet)         RX packets 484346  bytes 641850809 (612.1 MiB)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 368394  bytes 44259668 (42.2 MiB)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  rahman@debian:~$ sudo iwconfig  lo        no wireless extensions.  enp0s25   no wireless extensions.  wlp68s0b1  IEEE 802.11  ESSID:"3bdo"             Mode:Managed  Frequency:2.447 GHz  Access Point: 9C:C1:72:B0:3B:D4              Bit Rate=65 Mb/s   Tx-Power=30 dBm              Retry short limit:7   RTS thr:off   Fragment thr:off           Encryption key:off           Power Management:off           Link Quality=54/70  Signal level=-56 dBm             Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0           Tx excessive retries:4  Invalid misc:183   Missed beacon:0 Can Compound Topographic Index (CTI) / Topographic Wetness Index (TWI) produce negative values? I am calculating Topographic Wetness Index for a study area using SRTM DEM (90 and 30m).   I've seen several versions of TWI (CTI).  I have been using: TWI = ln(As +1 / tanB)       where As = catchment area, B = slope (degrees/radians??)  When I run this function, the output contains negative values (using slope in degrees and radians).  Are negative values acceptable? Or does this indicate an error in the analysis??  I understand the output should be scaled to 1-10, but negative values seems counter intuitive. Could someone explain what negative values could mean (due to flat areas, no data values?)  On a side not, the calculations are being run on on a very large area, which overaps several watersheds. Is it appropriate to run TWI over such a large extent? How do I download torrents? Why does Loki look "sick" when he first arrives on Earth? In the Avengers movie, why is Loki sweating and weak when he first arrives on Earth, in the SHIELD base? Switching languages in bibliography with biblatex I would like to have a bibliography with both Cyrillic and Latin and the main document language being English. How can I make biblatex to automatically switch between languages? (without using XeTeX as suggested by some) The minimal example returns an error if the main language is English. However, with the main language being Russian the document works.  \documentclass{article}  \usepackage[utf8]{inputenc} \usepackage[russian,english]{babel}  \usepackage[backend = biber,babel=other]{biblatex} \usepackage{csquotes} \addbibresource{library.bib}  \begin{document} %\selectlanguage{russian} %if the main document language is Russian the bibliography is compiled without any problem. This is a test. \parencite{Bara2006,Baranov2001}  \printbibliography  \end{document}   The .bib entries are  @book{Bara2006, address = {New York}, author = {Bara, Judith}, publisher = {Routledge}, title = {{English Citation entry}}, year = {2006} }  @book{Baranov2001, address = {Санкт-Петербугр}, author = {Баранов, Николай А}, title = {{Эволюция взглядов}}, year = {2001} } Allow flags on locked posts This is a  about how Unix operating systems report memory usage.   Similar Questions:                    I have production server that is running Debian 6.0.6 Squeeze  #uname -a  Linux debsrv 2.6.32-5-xen-amd64 #1 SMP Sun Sep 23 13:49:30 UTC 2012 x86_64 GNU/Linux   Every day cron executes backup script as root:  #crontab -e  0 5 * * * /root/sites_backup.sh &gt; /dev/null 2&gt;&amp;1   #nano /root/sites_backup.sh  #!/bin/bash str=`date +%Y-%m-%d-%H-%M-%S` tar pzcf /home/backups/sites/mysite-$str.tar.gz /var/sites/mysite/public_html/www mysqldump -u mysite -pmypass mysite | gzip -9 &gt; /home/backups/sites/mysite-$str.sql.gz cd /home/backups/sites/ sha512sum mysite-$str* &gt; /home/backups/sites/mysite-$str.tar.gz.DIGESTS cd ~   Everything works perfectly, but I notice that Munin's memory graph shows increase of cache and buffers after backup.  Then I just download backup files and delete them. After deletion Munin's memory graph returns cache and buffers to the state that was before backup.  Here's Munin graph:  Externally hosted image was a dead link. Best way to soft brute-force your own GPG/PGP passphrase? Can Minecraft be played by two players locally on the same account? I just bought Minecraft. Now, my brother wants to play with me but my Mom doesn't want to buy another. We use the same Wifi network. Can we do this? loading a view in popup hi i'm trying to display a view in a popup but unable to get a solution. i tried   colorbox node module popup views integration module   Is there any better way to display a view as a popup ? "Me and my wife" or "my wife and me" gedit "cannot open display" , on remote computer , using ssh - Ubuntu 12.04