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A couple of questions here on meta.physics (namely this one and this one that I could find) already asked for how to use tags on Phys.SE. The answers to these questions seemed to imply that it is not possible to automatically number the equations, like what happens in standard Latex for example with the equation envinronment.

I asked if this feature is possible on meta, and it turns out that it already exists in MathJax, as you can see from the answer to my question.

Here is an extract from the answer linked above:

This functionality already exists in MathJax. To enable it on an SE site, one would need to include either

equationNumbers: { autoNumber: "AMS" }

or

equationNumbers: { autoNumber: "all" }

in the TeX part of MathJax configuration options. I think the second option would be too aggressive: it would automatically number all displayed formulas in all posts on the site, which would often go against the intent of authors who created some equation numbers manually. The first option is reasonable: it would apply only to the displayed equations entered as AMS-LaTeX environments, e.g.

\begin{equation}
y=x^2 
\end{equation}

There aren't that many of those.

So the question now belongs here: should/could this feature be enabled on Phys.SE, to avoid painstakingly renumbering all equations in a post when adding/removing one in the middle of a text and similar things?

I would also think that an automatic numbering of equations by default would be useful as it would allow to easily reference not manually tagged equations posted by the OP, but this is probably not possible now as it would, if I understood correcly, mess up all the already manually numbered equations.

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    $\begingroup$ I assume the downvotes reflect the fact that people don't want this implemented; it's definitely good that someone brought it up, though. $\endgroup$ – David Z Feb 16 '15 at 19:25
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Consider a situation where someone asks for clarification about equation (4) in a comment, and then the post author adds a definition to clarify it just above it. Since the comment cannot be edited, the record will be confusing for newcomers and would be a not-really-worth-it pain to disentangle.

Automatic numbering works when you also have \label-ing and automatic \ref-erencing which can consistently point to the correct objects even when the equation numbers change. I think this is a bad idea on this site.

Additionally, note that there are close to 1k posts that already use the \begin{equation} notation, and 1.6k that use \begin{align}. We do not know whether their authors would like the tags, which could be quite intrusive. I have a few of those myself, and I'd not be that keen on this: when I use the align notation I'm half the time tagging things myself, and having automatic tags detracts from the emphasis given to the important equations by the manual tags.

To be honest, though, I just don't think there's a need. A long post might have 10-20 equations but only a couple of them are really worth numbering, and that's at the extremes and can be dealt with using manual \tags. I think we're getting along just fine and there isn't a use case for this.

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  • $\begingroup$ enabling the automatic numbering only for the equation envinronment mostly removes that issue: just add the additional equations using the classical $$equation$$ syntax $\endgroup$ – glS Feb 16 '15 at 16:11
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    $\begingroup$ @glance What if you explicitly want to refer to the $$equation$$ you edited in? Manually tag it (3')? You're jumping through hoops to keep things running precisely in the cases you care about. $\endgroup$ – Emilio Pisanty Feb 16 '15 at 17:08
  • $\begingroup$ For comments, the comment can just be deleted once the question changes. So the fact that automatic numbering might invalidate comments isn't really much of an argument against this proposal. $\endgroup$ – David Z Feb 16 '15 at 19:24
  • $\begingroup$ Just fyi, MathJax provides \ref, \eqref and \label, see docs.mathjax.org/en/latest/… $\endgroup$ – Peter Krautzberger Feb 17 '15 at 13:13
  • $\begingroup$ @PeterKrautzberger That's cool, but how would it work in practice? Is there a risk of collisions between answers? If you want to comment, how do you find the \label? Is it really worth the hassle? $\endgroup$ – Emilio Pisanty Feb 17 '15 at 13:44
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    $\begingroup$ I didn't mean to suggest this addresses the other points you've made. I just wanted to make sure the community has all the information it needs to discuss the question. $\endgroup$ – Peter Krautzberger Feb 17 '15 at 14:08
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I personally dislike auto-numbering of equations. They are not all important, and I only want to number the ones I refer back to. When you do that the fact that they have a tag gives the reader a head's up that this relation is not only useful in passing but will be back to haunt us illuminate another issue.

What I would like is to be able to refer to equations by label or tag. I know how to arrange that in real LaTeX, but haven't looked into how well it works in MathJax.

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