Why are MathJax images not displaying on my webpage?

[Redbelly98]

ah yes thanks for reminding me

It is my pleasure to remind to you

 

[quasar987]

In this thread, https://www.physicsforums.com/showthread.php?t=510385, does anyone know what might have triggered the appearance of the red part? I double checked and I didn't forget to write "\par" or anything. I even made a copy paste of the "{\partial f}" that appears in the LHS of the equation and the red part still appears in the LHS. The code I used is

\sum_i\frac{\partial f}{\partial x^i}\frac{d\varphi^i_x(t)}{dt}(0)=\sum_i\frac{\partial f}{\partial x^i}X^i(x)

 

[micromass]

In this thread, https://www.physicsforums.com/showthread.php?t=510385, does anyone know what might have triggered the appearance of the red part? I double checked and I didn't forget to write "\par" or anything. I even made a copy paste of the "{\partial f}" that appears in the LHS of the equation and the red part still appears in the LHS. The code I used is

\sum_i\frac{\partial f}{\partial x^i}\frac{d\varphi^i_x(t)}{dt}(0)=\sum_i\frac{\partial f}{\partial x^i}X^i(x)

Every 50 characters, the forum software automatically inserts a space. In this case, the \partial gets split into \par tial which doesn't exist. So it's better to leave some spaces and use

\sum_i\frac{\partial f}{\partial x^i}\frac{d\varphi^i_x(t)}{dt}(0) = \sum_i\frac{\partial f}{\partial x^i}X^i(x)

for example. This yields

$$\sum_i\frac{\partial f}{\partial x^i}\frac{d\varphi^i_x(t)}{dt}(0) = \sum_i\frac{\partial f}{\partial x^i}X^i(x)$$

 

[quasar987]

I see! :\

 

[Fredrik]

Any decision on new delimiters?

I'm bumping this question. Greg, did you decide that you don't want any new delimiters for LaTeX?

The default simple delimiters are:
$...$ for itex
$$...$$ for tex

This option is the only one that would make it possible to copy stuff without change between forum posts and LaTeX documents. However, most people feel that it's much more important to be able to type a dollar sign in posts about money without preceding it with a backslash or something. So I came up with two alternatives.

The simple option is:
££...££ for itex
$$...$$ for tex

Almost everyone has # and/or £ on the 3 key, and $ on the 4 key. Most (all?) of the ones who don't can still type those symbols easily.

The complicated option is:
££...££, $...$, §§...§§, ··...·· for itex.
$$...$$, ¢¢...¢¢ for tex.

The §,· and ¢ characters are minor improvements for Germans, Spaniards, and French Canadians respectively. The only advantage it has for them is that it allows them to use either Shift+3 for itex and Shift+4 for tex, or Alt Gr+3 for itex and Alt Gr+4 for tex, instead of e.g. Alt Gr+3 for itex and Shift+4 for tex.

Keyboard layouts at Wikipedia.

Note that one new "delimiter" (the option to use no delimiters at all in certain situations) has already been implemented. MathJax interprets stuff between "begin" and "end" statements as LaTeX, for example: \begin{align}\Lambda =\gamma\begin{pmatrix}1 & -v\\ -v & 1\end{pmatrix}, & & \gamma =\frac{1}{\sqrt{1-v^2}}.\end{align} This can be disabled if you prefer to force everyone to use itex and tex.

 

[Ben Niehoff]

The trouble with $...$ is that vBulletin parses posts using a regular expression engine. LaTeX syntax is too flexible to allow $...$ to be parsed using regular expressions. It requires a finite state machine instead.

Here's a simple explanation why: The best a regular expression algorithm can do is search for two $ signs with something in between. That is, a regular expression such as (Perl syntax)

\$(.*)\$

The reason you have to grab any sort of text that might appear between $ signs is because LaTeX syntax itself allows any sorts of characters to appear between $ signs. In particular, it allows spaces, periods, backslashes, even additional $ signs.

So, if someone is writing a post about money, and talks about $200 at one point, and then later mentions $5.35, then the vBulletin parser would grab the string

"200 at one point, and then later mentions "

and send it off to the LaTeX parser. Whoops.

The reason LaTeX itself can deal with the $ signs is because it doesn't use regular expressions.

Note, I have actually written an implementation of $...$ for vBulletin, but in order to work I added the additional requirement that the characters immediately adjacent to the $...$ cannot be spaces (if they are spaces, it interprets them as dollar signs). In the end I scrapped the idea, because I thought it would be too confusing to most people, especially given the disastrous attempts at LaTeX that we often see here.

 

[I like Serena]

THere's a simple explanation why: The best a regular expression algorithm can do is search for two $ signs with something in between. That is, a regular expression such as (Perl syntax)

\$(.*)\$

What about:

\$([^\$]*)\$

or

\$(.*?)\$

I've learned to always use pretty strict expressions in Perl to avoid such problems.

 

[Ben Niehoff]

What about:

\$([^\$]*)\$

or

\$(.*?)\$

I've learned to always use pretty strict expressions in Perl to avoid such problems.

Both of those would still fail on the example I gave (a sentence with two dollar amounts in it).

 

[Fredrik]

Greg isn't going to write any regular expressions. All he's going to do (if he chooses to do anything) is to find the line in the MathJax configuration file where the optional delimiters are specified, and type them in there. I think this makes it 100% certain that we would have the problem that Ben describes if we choose to use single dollar signs as LaTeX delimiters. I also think I read somewhere that the users can type \$3.50 when they want $3.50 to be displayed, but new members will still be pretty confused.

That's why I suggested that we use ££ instead of $.

 

[Ben Niehoff]

Why not choose \$ as the LaTeX delimiter? Then there is no collision with ordinary dollar signs.

Of course, it means you still can't copy and paste directly from LaTeX documents, but with your other solutions, you can't do that anyway.

Edit: Of course, then we'd have trouble writing Perl regular expressions in our posts! How does MathJax work; i.e., when does it run in the processing sequence? It seems to be a Javascript that runs on the completed page, which is long after the vBulletin parser processes the posts. In that case, I think we're stuck with 'itex' and 'tex'.

I would recommend against making the delimiter some random symbol. The $ sign is standardized already, but if it can't be the $ sign, it shouldn't be some other symbol.

 

[Fredrik]

Why not choose \$ as the LaTeX delimiter? Then there is no collision with ordinary dollar signs.

It's significantly harder to to type than ££.
(Edit: If you're that attached to standard usage, doesn't it also bother you that your suggestion is a complete reversal of the default "$ for itex", "\$ for dollar sign"?)

It seems to be a Javascript that runs on the completed page, which is long after the vBulletin parser processes the posts. In that case, I think we're stuck with 'itex' and 'tex'.

As I said, all that's required is a simple edit of a MathJax configuration file. (OK, maybe not if you specifically want to use \$ as a delimiter).

 

[vela]

I would recommend against making the delimiter some random symbol. The $ sign is standardized already, but if it can't be the $ sign, it shouldn't be some other symbol.

Why not? What's wrong with using something like ##?

 

[Fredrik]

The simple option is:
££...££ for itex
$$...$$ for tex

Almost everyone has # and/or £ on the 3 key, and $ on the 4 key. Most (all?) of the ones who don't can still type those symbols easily.

The complicated option is:
££...££, $...$, §§...§§, ··...·· for itex.
$$...$$, ¢¢...¢¢ for tex.

The §,· and ¢ characters are minor improvements for Germans, Spaniards, and French Canadians respectively. The only advantage it has for them is that it allows them to use either Shift+3 for itex and Shift+4 for tex, or Alt Gr+3 for itex and Alt Gr+4 for tex, instead of e.g. Alt Gr+3 for itex and Shift+4 for tex.

Keyboard layouts at Wikipedia.

I had another look a the keyboard layout page. I had forgotten that ££ is a bad option for people with a US keyboard. $is better for them. But most of the rest of the world should prefer ££ (based on the location on the keyboard), so here's a third option:$...## or ££...££ for itex
$$...$$ for tex

 

[vela]

$...$ or ££...££ for itex
$$...$$ for tex

I'd modify that slightly to $…$ and ££…££ for itex.

 

[Redbelly98]

I think you both mean the same thing.

A person could use either $...$ or ££...££ for itex, and it would work.

Both $…$ and ££…££ would work for itex.

 

[Juqon]

Why is my latex code not processed?
[itex]\frac{i \hbar t}{m}[\itex]
[itex]\frac{i\hbart}{m}[\itex]
[itex]\frac{i\hbar t}{m}[\itex]

 

[Fredrik]

Why is my latex code not processed?

Your closing itex tags are wrong. Use /, not \.

 

[Juqon]

Oh, of course, thank you! :)

 

[Juqon]

And what about this code?

https://www.physicsforums.com/showpost.php?p=3461733&postcount=6

 

[Redbelly98]

And what about this code?

https://www.physicsforums.com/showpost.php?p=3461733&postcount=6

As a start, you need to put some spaces in with that code. After 50 consecutive characters without a space, the processor will automatically insert a space.

By the way, you don't need the {} brackets when they surround a single character, i.e. t^{2} can be simply replaced with t^2. That will give you fewer brackets, and be easier to debug in case the numbers of {'s and }'s don't match.

 

[Borek]

And what about this code?

https://www.physicsforums.com/showpost.php?p=3461733&postcount=6

First - split it into separate equations replacing \\ with [noparse][/tex][tex][/noparse] - you will see some of the equations are parsed correctly, while others are not.

 

[Fredrik]

And what about this code?

https://www.physicsforums.com/showpost.php?p=3461733&postcount=6

What the other two guys said. As an alternative to multiple tex tags, use the align environment. That will make the \\ code work. Like this: \begin{align}
a &= b\\
&=c
\end{align} Tex tags are actually not necessary when the latex code starts with a begin statement, and ends with the corresponding end statement.

Also, please don't post equations with lines that are that long. They are seriously annoying in a browser window. So please insert a few extra \\ to make the lines shorter.

 

[Juqon]

Absolutely right, and the space broke the command \r ight.
And that with the new line separation was very motivating.
Very helpful, thanks!

 

[paul-g]

Hello!
I am writing because I do not know how to write the following formula in MathJax

I have read this entire thread and information about extracurricular parentheses, but in this case it's not that simple.

Did you have problems with habits relating to of the old system?

What about tables? It is not possible to create them?

$\small\overbrace{a,...,a}^{\mbox{k a's}}, \underbrace{b,...,b}_{\mbox{l b's}}\hspace{10} \large\underbrace{\overbrace{a...a}^{\mbox{k a's}}, \overbrace{b...b}^{\mbox{l b's}}}_{\mbox{k+l elements}}$

$\small\overbrace{a,...,a}^{\mbox{k a's}}, \underbrace{b,...,b}_{\mbox{l b's}}\hspace{10pt} \large\underbrace{\overbrace{a...a}^{\mbox{k a's}}, \overbrace{b...b}^{\mbox{l b's}}}_{\mbox{k+l elements}}$


$\left[ \frac{X}{Y}\right ]$

On mathtex that gives

 

[Fredrik]

I am writing because I do not know how to write the following formula in MathJax

You can't open with "tex" and close with "itex" or vice versa. You need to specify a unit for the hspace command. Note sure about the tables.

$$\small\overbrace{a,...,a}^{\mbox{k a's}}, \underbrace{b,...,b}_{\mbox{l b's}}\hspace{10pt} \large\underbrace{\overbrace{a...a}^{\mbox{k a's}}, \overbrace{b...b}^{\mbox{l b's}}}_{\mbox{k+l elements}}$$
$$\left[ \frac{X}{Y}\right ]$$

 

[paul-g]

The fact that I forgot to define the / hspace number of the unit, but it worked for MathTex.

Thank you anyway.

I will experiment a bit with the tables.