View source for Testwiki:Help desk/Archives/2014 November 3

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= November 3 =

== Absence of comment in a "GA Reassessment" ==

There are about two weeks, [[Talk:Fursuit/GA1|I questioned the quality of the article Fursuit]], if it really deserves mention of "good article". I sent message to the main editors of the page, but only one replied. I wonder what I should do to be some's conclusion. [[User:Keplerbr|Keplerbr]] ([[User talk:Keplerbr|talk]]) 05:41, 3 November 2014 (UTC)

:<small>Hello, {{U|Keplerbr}}. Not an answer to your question, but please note that readers who do not speak French will probably not understand "There are about two weeks". The English for "Il y a deux semaines" is "Two weeks ago". I don't usually comment on people's English, but where I believe I recognise a foreign idiom which will not be understood in English I think it is helpful to do so. --[[User:ColinFine|ColinFine]] ([[User talk:ColinFine|talk]]) 23:30, 3 November 2014 (UTC)</small>

== Help:Cite errors/Cite error ref no input ==


<!-- This request was passed from a Cite error help page -->
I edited the Uri Milstein page and included proper references, but got the message that they had no content.[[User:Dale Stern|Dale Stern]] ([[User talk:Dale Stern|talk]]) 06:59, 3 November 2014 (UTC)
:{{la|Uri Milstein}}
:I've fixed the syntax for you; you had mistyped a {{tag|ref}} pair. -- [[User:John of Reading|John of Reading]] ([[User talk:John of Reading|talk]]) 07:14, 3 November 2014 (UTC)

== Reverting vandalism ==

Hi, I'm pcfan500. I am just wondering if anyone has any tips for reverting vandalism on Wikipedia. I am a new user and one of the main purposes of my prescence on Wikipedia is to remove damage from articles. Thanks! [[User:Pcfan500|Pcfan500]] ([[User talk:Pcfan500|talk]]) 07:06, 3 November 2014 (UTC)

:I think everything you could ever want to know about that is covered in [[Wikipedia:Vandalism]]. Unless you have specific questions, I wouldn't know what "tips" to give. &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 07:14, 3 November 2014 (UTC)
:Hi [[User:Pcfan500|Pcfan500]]!  Vandalism is usually made my IP's or anonymous users.  You can also check the [[Special:Tags]] for vandalism or non-constructive edits.  Hope this helps!  [[User:Eurodyne|Eurodyne]] ([[User talk:Eurodyne|talk]]) 15:28, 3 November 2014 (UTC)

== Identify a spider ==

what if i just have a question about the natural world around me and i don't want to have to sign into a program to ask it?

LIKE - i saw a big green spider and i can't seem to see it online or in books or through my fellow scientist colleagues 

i did not photograph it.  i went into the woods with nothing.  

I was in georgia close to savannah.

i want to know if anyone online knows of this spider or if it is the first to be seen.  the internet is a big place but it seems you have to login and i don't know why it seems annoying.

* the spiders was as big as a texas sized tarantula, but not harry.
* it had a green belly, or the big bottom part of the body and small black spots.
* it's web was between two massive trees and it sat in the middle of it.
i was very intimidated and backed away slowly.

how could i search for something like this on your website.

thank you very much for this forum.  <span style="font-size: smaller;" class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/172.2.65.116|172.2.65.116]] ([[User talk:172.2.65.116|talk]]) 07:23, 3 November 2014 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

:The best way to find the answer to that question at Wikipedia is probably to ask it at [[Wikipedia:Reference desk/Science|the science desk]]. But the web is a rich information resource, and you might have better luck investigating [https://www.google.com/search?client=firefox-a&hs=tsY&rls=org.mozilla%3Aen-US%3Aofficial&channel=fflb&q=identifying+spider&oq=identifying+spider&gs_l=serp.12...0.0.0.3957.0.0.0.0.0.0.0.0..0.0....0...1c..58.serp..0.0.0.6NS--f4dQXw these Google hits]. I'm sure many of them do not require a login. &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 07:51, 3 November 2014 (UTC)

== At which project should I report this? ==

Dear editors:  This article was copied out of AfC by its creator without being reviewed. It needs serious work.  I've removed dozens of inappropriate links and self-references, but I need to recruit help from someone who understands this subject. I haven't found reliable sources, but I don't really know where to look.  Can someone suggest which Wikiproject would be the best one at which to post a plea?  &mdash;[[User:Anne Delong|Anne Delong]] ([[User talk:Anne Delong|talk]]) 09:38, 3 November 2014 (UTC)
:It would help if you told us what the page was.  <span style="font-family:monospace;">[[User:Dismas|Dismas]]</span>|[[User talk:Dismas|<sup>(talk)</sup>]] 09:39, 3 November 2014 (UTC)
:Hi Anne, for the article [[Emilia Telese]], you can best go to [[Wikipedia:WikiProject Arts|Wikiproject Arts]] and its subproject [[Wikipedia:WikiProject Visual arts|Wikiproject Visual arts]]. - Sincerely, [[User:Taketa|Taketa]] ([[User talk:Taketa|talk]]) 09:55, 3 November 2014 (UTC)

== Problem With Shorts on [[Cyprus national rugby union team]] ==

on the [[Cyprus national rugby union team]] page I have updated the kit and I decided to put the previous kt in in 'kit evolution' segment. everything was fine with the kit except for the shorts on both kits which seem to be out of place. I believe the shorts are the correct size and do not believe I have any formatting errors how ever if someone could help me it would be greatly appreciated.  <small><span class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Grickles|Grickles]] ([[User talk:Grickles|talk]] • [[Special:Contributions/Grickles|contribs]]) 11:09, 3 November 2014 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

:Other shorts at [//commons.wikimedia.org/w/index.php?title=Category:Football_kit_shorts&filefrom=Kit+shorts+cy] are 100x36 with the shorts in the middle. Yours are 50x36 with the shorts taking up all the space. [[User:PrimeHunter|PrimeHunter]] ([[User talk:PrimeHunter|talk]]) 11:56, 3 November 2014 (UTC)

== UCL wiki page ==

Hi,

Please could you add a link to the Faculty of Medical Sciences, as in the Organisation and administration section? The link is http://www.ucl.ac.uk/medical-sciences/ 

Thanks, Emily.  <span style="font-size: smaller;" class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/193.60.248.17|193.60.248.17]] ([[User talk:193.60.248.17|talk]]) 12:47, 3 November 2014 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->
:Probably not per [[WP:OFFICIAL]]. We are not a linkwall. -- [[User talk:TheRedPenOfDoom|<span style="color:red;;;">TRPoD <small>aka The Red Pen of Doom</small></span>]] 13:04, 3 November 2014 (UTC)

== Website citation question ==

If an individual appeared in a movie could that movie's own website be considered a valid citation? I would think this would be more promotional than anything and would need a third party source devoid of anything to do with said production.[[User:Cthwikia|Cthwikia]] ([[User talk:Cthwikia|talk]]) 16:34, 3 November 2014 (UTC)
:Such a site can't be used as evidence of the film's notability, but it ''can'' be used to demonstrate basic facts, such as casting.  [[User:Rojomoke|Rojomoke]] ([[User talk:Rojomoke|talk]]) 17:56, 3 November 2014 (UTC)

::OK thanks.[[User:Cthwikia|Cthwikia]] ([[User talk:Cthwikia|talk]]) 18:22, 3 November 2014 (UTC)

== How do I get an image (IUPAC) file? ==

For 5-hydroxyicosatetraenoic acid and 5-oxo-eicosatetraenoic acid, the image (IUPAC) file for 5-hydroxyicosatetraenoic acid but not 5-oxo-eicoatetraenoic acid is in place.  How can I get and place the image(IUPAC) file for 5-oxo-eicoatetreaenoic acid?  Thanks.[[User:Joflaher|Joflaher]] ([[User talk:Joflaher|talk]]) 16:39, 3 November 2014 (UTC)
:Are you taking about the image of the structure? I'm not sure how you would add it, but I believe the two compounds should have separate infoboxes. You may want to ask over at [[WP:CHEMS]].[[User:Naraht|Naraht]] ([[User talk:Naraht|talk]]) 18:47, 3 November 2014 (UTC)

:{{u|Joflaher}} I found an online image, [http://www.lipidmaps.org/data/LMSDRecord.php?Mode=View&LMID=LMFA03060057&ViewType=GIF]. Read the [http://www.lipidmaps.org/about/terms_of_use.html TOS] before reusing the image. --[[User:Fauzan|<span style="color:#2F4F4F;">Fauzan</span>]]<sup style="margin-left:+0.5ex">[[User talk:Fauzan#top|<span style="color:#BDB76B;">✆ talk</span>]]</sup><sub style="margin-left:-4.6ex">[[Special:EmailUser/Fauzan|<span style="color:#BDB76B;">✉ mail</span>]]</sub> 20:38, 3 November 2014 (UTC)

== How do I report a bug? ==

My main page stopped updating on Oct 31. I'm not sure if this is some sort of local bug or more widespread. In any case I need to know how and to whom to report it. 

I'm running Safari 6.1 on OS X, 10.8.5  <small class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/75.104.137.20|75.104.137.20]] ([[User talk:75.104.137.20|talk]]) 17:58, 3 November 2014 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

:What do you mean by "My main page"? Is it about [[Main Page]]? Have you tried to [[WP:BYPASS|clear your cache]]? [[User:PrimeHunter|PrimeHunter]] ([[User talk:PrimeHunter|talk]]) 18:04, 3 November 2014 (UTC)
:{{ec}} Bug reports are filed over at [http://bugzilla.wikimedia.org bugzilla.wikimedia.org], which you can learn more about [https://www.mediawiki.org/wiki/Bugzilla here].
:However, the issues you are facing don't sound like a bug. You most likely have to purge either the server's or your browser's cache. Take a look at [[Wikipedia:FAQ/Main_Page#Why_is_the_Main_Page_not_updating.3F|Wikipedia's Main Page FAQ]] for more info, and instructions/links on how to do that. '''~''[[User:SuperHamster|<span style="color:#07517C">Super</span>]]''[[User:SuperHamster|<span style="color:#6FA23B">Hamster</span>]]''' <small>[[User talk:SuperHamster|Talk]] [[Special:Contribs/SuperHamster|Contribs]]</small> 18:13, 3 November 2014 (UTC)

== Replace obsolete picture ==

Regarding missing image of “1938 Ohio License Tag” on site:  [[Vehicle registration plates of Ohio]]

I have found an image suitable to replace the “blank image” located at: [[:File:Blank License Plate Shape.jpg]]

I have successfully uploaded the JPEG of the appropriate image to:
[[:File:Ohio 1938 NWT Centennial.jpg]]

I have followed online instructions the best I am able, but I have been unable to add the image to the article, AND unable to “UPDATE” the blank JPEG with my replacement that I found on www.ebay.com  and personally edited appropriately to make the “swap.”

Will you either “make the replacement” for me or give me detailed directions of how to do it?  My preference would be for you to do it.  I am not interested in getting credit for it.  <small><span class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Mr.Gale.B|Mr.Gale.B]] ([[User talk:Mr.Gale.B|talk]] • [[Special:Contributions/Mr.Gale.B|contribs]]) 18:23, 3 November 2014 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
:Hi {{ping|Mr.Gale.B}} You can update the image by simply replacing the file name in the table (i.e. replace <code>Blank_License_Plate_Shape.jpg</code> with <code>Ohio_1938_NWT_Centennial.jpg</code>). However, there is a bigger problem - the image you uploaded appears to not be properly sourced or licensed. All images on the Wikimedia Commons should be [[Wikipedia:Non-free content|freely licensed]] by their original authors. You cannot take another person's photograph and upload it to the Commons if they have not appropriately licensed it. Stemming off of this, proper attribution needs to be provided for the original author. '''~''[[User:SuperHamster|<span style="color:#07517C">Super</span>]]''[[User:SuperHamster|<span style="color:#6FA23B">Hamster</span>]]''' <small>[[User talk:SuperHamster|Talk]] [[Special:Contribs/SuperHamster|Contribs]]</small> 18:33, 3 November 2014 (UTC)
:P.S. Not to complicate things, but to expand on this, it is also true that a simple picture of a public domain work also falls into the public domain. ''If'' the license plate falls in the public domain, it could be argued that the image you have uploaded is also in the public domain. I'm not sure if all Ohio license plates are in the public domain, or if the license plate is complicated enough to warrant copyright, so that may be a good question to bring up at [[Wikipedia:Media copyright questions]]. If the plate does qualify as being in the public domain, proper sourcing should still be included, however. '''~''[[User:SuperHamster|<span style="color:#07517C">Super</span>]]''[[User:SuperHamster|<span style="color:#6FA23B">Hamster</span>]]''' <small>[[User talk:SuperHamster|Talk]] [[Special:Contribs/SuperHamster|Contribs]]</small> 18:50, 3 November 2014 (UTC)

==Book problem==
Hi

Every time I try to create a book and come back to it later, it has gone. I save, I give it a name. What am I doing wrong?

[[User:Brentsimpson2014|Brentsimpson2014]] ([[User talk:Brentsimpson2014|talk]]) 19:13, 3 November 2014 (UTC)
:It might be so that it is not about anything [[WP:NOTABLILITY|notable]]? Or maybe you don't properly source it with [[WP:RS|reliable sources]]. --<span style="text-shadow:#396 0.2em 0.2em 0.5em; class=texhtml">[[User:TopGun|<b style="color:#060">lTopGunl</b>]] ([[User talk:TopGun|<b style="color:#000">talk</b>]])</span> 19:57, 3 November 2014 (UTC)

:I assume this is about the feature at [[Help:Books]]. [[Special:Contributions/Brentsimpson2014]] shows you have saved [[User:Brentsimpson2014/Books/Pirates]]. Is that it? [[User:PrimeHunter|PrimeHunter]] ([[User talk:PrimeHunter|talk]]) 20:07, 3 November 2014 (UTC)

:The OP is probably referring to a [[Wikipedia:Book]]. {{u|Brentsimpson2014}}, after logging in, on the top right among many useful links, there "Contributions" just before "Log out". Clicking on it will lead you [[Special:Contributions/Brentsimpson2014|here]], which list all your edits while logged in. From there you can see that you made three edits to the page [[User:Brentsimpson2014/Books/Pirates]]. For future reference, you can create your userpage, [[User:Brentsimpson2014]], and place the text <code><nowiki>[[User:Brentsimpson2014/Books/Pirates]]</nowiki></code> to save a link to the page. You can access your user page by clicking on your name, the first link on the top right. --[[User:Fauzan|<span style="color:#2F4F4F;">Fauzan</span>]]<sup style="margin-left:+0.5ex">[[User talk:Fauzan#top|<span style="color:#BDB76B;">✆ talk</span>]]</sup><sub style="margin-left:-4.6ex">[[Special:EmailUser/Fauzan|<span style="color:#BDB76B;">✉ mail</span>]]</sub> 20:19, 3 November 2014 (UTC)
::<small>Did not notice [[User:PrimeHunter|you]]! --[[User:Fauzan|<span style="color:#2F4F4F;">Fauzan</span>]]<sup style="margin-left:+0.5ex">[[User talk:Fauzan#top|<span style="color:#BDB76B;">✆ talk</span>]]</sup><sub style="margin-left:-4.6ex">[[Special:EmailUser/Fauzan|<span style="color:#BDB76B;">✉ mail</span>]]</sub> 20:23, 3 November 2014 (UTC)</small>

==[[Bat bomb]]==
{{Re: your entry for “Bat Bomb”. I am the sole surviving crew member of this World War II effort and the author of the only factual book on the subject. I note an inappropriate statement in your piece that should be corrected.

At the end of your description of the project is the statement: “Lovell also mentioned that bats during testing were dropping to the ground like stones.” This is misleading as it implies that the weight carrying tests were negative. In fact, in order to determine the weight carrying capacity of the bats in flight, it was necessary to find just how much they couldn’t carry--a basic factor in such an investigation.  Further tests showed the weight they could carry.

Lovell’s negative view at the beginning was not a deterrent, as the project was authorized and went on to  a successful conclusion and was stopped only by the
invention of the atomic bomb.}}  <small class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/75.82.165.59|75.82.165.59]] ([[User talk:75.82.165.59|talk]]) 20:43, 3 November 2014 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

:The sentence in question cites a book, including the page number. If you can provide a [[WP:RS|reliable source]] for your proposed change, you are welcome to make the change yourself, or someone here might be willing to make the change for you. You can also bring up the issue on the article's talk page, [[Talk:Bat bomb|here]]. But, basically, Wikipedia is about reliable published sources, not personal knowledge. Best of luck,&#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 21:01, 3 November 2014 (UTC)

== Edit triggered a filter ==

Hi, 

I just tried to edit the stub article on "Arrowhead matrix"
and got the response below. I would like to have an explatiation what is wrong with the article, so that I could revise it.
My edit is below, too.

Best regards, Ivan Slapnicar

{{collapse top}}
Your edit has triggered a filter designed to warn editors, organisations and companies against using Wikipedia as an advertising medium.

Wikipedia is foremost an encyclopedia, and not a vehicle for advertising or promoting organisations, companies or individuals. If that is not your intent, we apologize. However, before you continue you may wish to review Wikipedia's guidelines on conflict of interest and external links, as these may help you decide whether the information you want to include is appropriate for Wikipedia. You may also wish to check Wikipedia's username policy, which prohibits promotional usernames. Please feel free to ask at the Help Desk if you have any questions.
If you're sure you still want to make this edit, go to the bottom of this page and click 'Save page' again, and it will be submitted as is. If you believe you received this message in error, you may report this error.

Here is the edit that I submitted (but not finalized):


In the [[mathematical]] field of [[linear algebra]], an '''arrowhead matrix''' is a square [[matrix (mathematics)|matrix]] containing zeros in all entries except for the first row, first column, and main diagonal.<ref name="OLS90">{{cite journal |last1=O'Leary |first1=D. P. |last2=Stewart |first2=G. W. |title=Computing the eigenvalues and eigenvectors of symmetric arrowhead matrices |journal=Journal of Computational Physics| year=1990 |pages=497–505|volume=90 |issue=2 |doi=10.1016/0021-9991(90)90177-3}}</ref>
<ref name="JSSB15">{{cite journal |doi=10.1016/j.laa.2013.10.007 |last1=Jakovcevic Stor |first1=Nevena |last2=Slapnicar |first2=Ivan |last3=Barlow |first3=Jesse L. |title=Accurate eigenvalue decomposition of real symmetric arrowhead matrices and applications |journal=Linear Algebra and Its Applications|volume=464|year=2015|pages=62–89}}{{Cite journal| arxiv=1302.7203 |year=2013|author1=Nevena Jakovcevic Stor |title=Accurate eigenvalue decomposition of arrowhead matrices and applications |journal=Linear Algebra and its Applications |volume=464 |pages=62 |last2=Slapnicar |first2=Ivan |last3= Barlow |first3=Jesse L. |doi=10.1016/j.laa.2013.10.007 }}</ref> In other words, the matrix has the form
:<math>
A=\begin{bmatrix}
\,\! *&*&*&*&* \\
\,\! *&*&0&0&0 \\
\,\! *&0&*&0&0 \\
\,\! *&0&0&*&0 \\
\,\! *&0&0&0&*
\end{bmatrix}.
</math>
Any symmetric permutation of the arrowhead matrix, <math>P^T A P</math>, where ''P'' is a [[permutation matrix]] is a
'''(permuted) arrowhead matrix'''. Real symmetric arrowhead matrices are used in some algorithms for finding of [[eigenvalue]]s and [[eigenvector]]s.<ref>{{cite journal|doi=10.1137/S0895479892241287|title=A Divide-and-Conquer Algorithm for the Symmetric Tridiagonal Eigenproblem|year=1995|last1=Gu|first1=Ming|last2=Eisenstat|first2=Stanley C.|journal=SIAM Journal on Matrix Analysis and Applications|volume=16|pages=172}}</ref>

{{fake heading|Real symmetric arrowhead matrices}}

Let ''A'' be a real symmetric (permuted) arrowhead matrix of the form 
:<math>
A=\left[
\begin{array}{cc}
D & z \\
z^{T} & \alpha
\end{array}
\right],
</math>
where <math>D=\mathop{\mathrm{diag}}(d_{1},d_{2},\ldots ,d_{n-1})</math> is diagonal matrix of order ''n-1'',
<math>z=\begin{bmatrix}
\zeta _{1} & \zeta _{2} & \cdots & \zeta _{n-1}
\end{bmatrix}^T</math> is a vector and <math>\alpha</math> is a scalar. Let
:<math>
A=V\Lambda V^{T}
</math>
be the [[Eigendecomposition of a matrix|eigenvalue decomposition]] of ''A'', where 
<math>\Lambda =\mathop{\mathrm{diag}}(\lambda _{1},\lambda _{2},\ldots ,\lambda_{n})</math>
is a diagonal matrix whose diagonal elements are the [[eigenvalue]]s of ''A'', and
<math>V=\begin{bmatrix}v_{1} & \cdots & v_{n} \end{bmatrix}</math>
is an orthonormal matrix whose columns are the corresponding [[eigenvector]]s. The following holds:
* If <math>\zeta_i=0</math> for some ''i'', then the pair <math>(d_i,e_i)</math>, where <math>e_i</math> is the ''i''-th [[standard basis]] vector, is an eigenpair of ''A''. Thus, all such rows and columns can be deleted, leaving the matrix with all <math>\zeta_i\neq 0</math>.
*  The [[Min-max_theorem#Cauchy_interlacing_theorem|Cauchy interlacing theorem]] implies that the sorted eigenvalues of $A$ interlace the sorted elements <math>d_i</math>: if <math>d_1 \geq d_2\geq \cdots\geq d_{n-1}</math> (this can be attained by symmetric permutation of rows and columns without loss of generality), and if <math>\lambda_i</math>s are sorted accordingly, then <math>
\lambda_1\geq d_1\geq \lambda_2\geq d_2\geq \cdots \geq \lambda_{n-1} \geq d_{n-1} \geq \lambda_n
</math>.
* If <math>d_{i}=d_{j}</math>, for some <math>i\neq j</math>, the above inequality implies that <math>d_{i}</math> is an eigenvalue of ''A''. The size of the problem can be reduced by annihilating <math>\zeta_j</math> with a [[Givens rotation]] in the <math>(i,j)</math>-plane and proceeding as above.

{{fake heading|Eigenvalues and eigenvectors}}

Symmetric arrowhead matrix is '''irreducible''' if <math>\zeta_i\neq 0</math> for all ''i'' and  <math>d_{i}\neq d_{j}</math> for all <math>i\neq j</math>. The [[eigenvalue]]s of an irreducible real symmetric arrowhead matrix are the zeros of the [[Characteristic_polynomial#Characteristic_equation|secular equation]]
:<math>
f(\lambda )=\alpha -\lambda -\sum_{i=1}^{n-1}\frac{\zeta _{i}^{2}}{
d_{i}-\lambda }\equiv \alpha -\lambda -z^{T}(D-\lambda I)^{-1}z=0
</math>
which can be, for example, computed by the [[bisection method]].
The corresponding [[eigenvector]]s are equal to 
:<math>
v_{i}=\frac{x_{i}}{\| x_{i}\| _{2}}, \quad x_{i}=
\begin{bmatrix}
\left( D-\lambda _{i}I\right)^{-1}z \\
-1
\end{bmatrix}, \quad i=1,\ldots ,n.
</math>
Direct application of the above formula may yield eigenvectors which are not numerically sufficiently orthogonal.<ref name="OLS90"/> 
The forward stable algorithm which computes each eigenvalue and each component of the corresponding eigenvector to almost full accuracy is described in <ref name="JSSB15"/>. The [[Julia_(programming_language)|Julia]] version of the software is available.<ref>[https://github.com/ivanslapnicar/Arrowhead.jl "Arrowhead.jl"]</ref>

{{fake heading|Inverses}}
Let ''A'' be an irreducible real symmetric arrowhead matrix.
If <math>d_i=0</math> for some ''i'', the inverse is a permuted irreducible real symmetric arrowhead matrix:
:<math>
A^{-1}=\begin{bmatrix}
D_{1}^{-1} & w_{1} & 0 & 0 \\
w_{1}^{T} & b & w_{2}^{T} & 1/\zeta _{i} \\
0 & w_{2} & D_{2}^{-1} & 0 \\
0 & 1/\zeta _{i} & 0 & 0
\end{bmatrix}
</math>
where
:<math>
\begin{alignat}{2}
D_1& =\mathop{\mathrm{diag}}(d_{1},d_{2},\ldots ,d_{i-1}), \\  
D_2&=\mathop{\mathrm{diag}}(d_{i+1},d_{i+2},\ldots ,d_{n-1}),\\
z_1&=\begin{bmatrix} \zeta _{1} & \zeta _{2} & \cdots & \zeta _{i-1}\end{bmatrix}^T, \\ 
z_2&=\begin{bmatrix} \zeta _{i+1} & \zeta _{i+2} & \cdots & \zeta _{n-1}\end{bmatrix}^T,\\
w_{1}&=-D_{1}^{-1}z_{1}\frac{1}{\zeta _{i}},\\
w_{2}&=-D_{2}^{-1}z_{2}\frac{1}{\zeta _{i}},\\
b&=\frac{1}{\zeta _{i}^{2}}\left(
-a+z_{1}^{T}D_{1}^{-1}z_{1}+z_{2}^{T}D_{2}^{-1}z_{2}\right).
\end{alignat}
</math>
<br />
If <math>d_i\neq 0</math> for all ''i'', the inverse is a ''rank-one modification of a diagonal matrix'' ('''diagonal-plus-rank-one''' matrix or '''DPR1'''):
:<math>
A^{-1}=\begin{bmatrix} D^{-1} &  \\ & 0\end{bmatrix}+\rho uu^{T},
</math>
where
:<math>
u=\begin{bmatrix} D^{-1} z \\ -1\end{bmatrix},\quad \rho =\frac{1}{\alpha-z^{T}D^{-1}z}.
</math>

{{fake heading|References}}
{{Reflist}}

[[:Category:Matrices]]

<nowiki>{{Linear-algebra}}</nowiki>
{{collapse bottom}}

[[User:Ivanslapnicar|Ivanslapnicar]] ([[User talk:Ivanslapnicar|talk]]) 22:32, 3 November 2014 (UTC)
:Hi {{u|Ivanslapnicar}}. Did you do this: "If you're sure you still want to make this edit, go to the bottom of this page and click 'Save page' again, and it will be submitted as is."? --[[User:NeilN|<b style="color:navy">Neil<span style="color:red">N</span></b>]] <sup>[[User talk:NeilN|<i style="color:blue">talk to me</i>]]</sup> 22:58, 3 November 2014 (UTC)

:Clearly there's no advertising in that, so it's an error, and you would override as described above. The message ends with "If you believe you received this message in error, you may report this error." I'm guessing the words "report this error" were a link for reporting the error. Did you click it? &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 23:01, 3 November 2014 (UTC)

:We refactored your question, as the content was rather overwhelming.
:The issue is that reference 2 includes your name, thus it triggered the edit filter as it appears you have a close relationship to the subject. You should discuss this on the article talk page to clear yourself of a conflict of interest. --<span style="color:Turquoise">''''' &nbsp;[[User:Gadget850|Gadget850]]'''''<sup>[[User talk:Gadget850|&nbsp;''talk'']]</sup></span> 23:02, 3 November 2014 (UTC)

:{{ec}}I don't altogether understand the above. I don't know enough math<s>s</s> to understand the material you wanted to add, but I can see that it is not advertising. So I used it to replace the rather short article, whose history shows that you had never edited it. I saw no warning message. I may have messed up the categories it was in, and I am suspicious of the line that reads <nowiki>{{fake heading|References}}</nowiki>. [[User:Maproom|Maproom]] ([[User talk:Maproom|talk]]) 23:08, 3 November 2014 (UTC)

::I'd suggest reading what Gadget850 said. &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 23:14, 3 November 2014 (UTC)
::After waiting ten minutes, I took the liberty of reverting your edits based on what Gadget850 said. &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 23:26, 3 November 2014 (UTC)

:::Click "filter log" at [[Special:Contributions/Ivanslapnicar]] to see "User adds link containing username", as Gadget850 said. I have asked for input at [[Wikipedia talk:WikiProject Mathematics#Arrowhead matrix]]. [[User:PrimeHunter|PrimeHunter]] ([[User talk:PrimeHunter|talk]]) 00:11, 4 November 2014 (UTC)

::::He added only one such link (the other was there already), to a downloadable free software package for handling arrowhead matrices. I considered that was justified. [[User:Maproom|Maproom]] ([[User talk:Maproom|talk]]) 00:18, 4 November 2014 (UTC)

{{od}}Just FYI, [https://en.wikipedia.org/w/index.php?title=Arrowhead_matrix&diff=632361474&oldid=632346470 an IP reverted my revert], no editsum, no other history as an IP. The IP geolocates to MIT. I'm not going to edit war over this, but keeping things up to date. &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 01:54, 4 November 2014 (UTC)
:COI editing is not forbidden by Wikipedia policies. On [[WP:COI]], one reads {{tq|Editors with COIs who wish to edit responsibly are strongly encouraged to follow Wikipedia policies and best practices scrupulously.}} Here, we are faced to a new editor, undoubtedly expert of the subject, who has tried, with good faith to transform a stub into an article. Reading his version of the article, it appears that the COI lies only in the two last sentences of section "Eigenvalues and eigenvectors". The remainder of the added content consists of generalities that can certainly been sourced by other sources. IMO, the two COI sentences deserve to be kept (with small copy edit, such as replacing "the" by "a"), as sourced in an article published in a major journal of linear algebra. Wikipedia, is strongly lacking of expert editors in mathematics, specially in advanced linear algebra. Above discussion has not [[WP:AGF|assumed good faith]] and seems aimed to discourage a new expert editor of continuing. I strongly suggest to close it. [[User:D.Lazard|D.Lazard]] ([[User talk:D.Lazard|talk]]) 06:51, 4 November 2014 (UTC)

::Good faith was never doubted, only good judgment. From [[WP:AGF]]: {{tq|Be careful about citing this principle too aggressively. Just as one can incorrectly judge that another is acting in bad faith, so too can one mistakenly conclude that bad faith is being assumed; exhortations to "Assume Good Faith" can themselves reflect negative assumptions about others.}} &#8209;&#8209;[[User:Mandruss|<span style="color:#8E8278;">'''''Mandruss'''''</span>]]&nbsp;[[User talk:Mandruss|<span style="color:#AAA;">&#9742;</span>]] 07:02, 4 November 2014 (UTC)