Debugging Latex Equations: Tips and Tools for Troubleshooting

[John Creighto]

\left(\frac{\partial \mathcal L(a_1,…a_n, …;\dot a_1,..,\dot a_n, …;t)}{\partial a_i}\right) - \left(\frac{d}{dy} \frac{\partial \mathcal L(a_1,…a_n, …;\dot a_1,..,\dot a_n, …;t)}{\partial \dot a_i}\right) = 0 \quad \text{for } i = 1, \dots, n, i \neq j

The above equation works on this form but won't work on my wordpress blog (see Lagrangian Mechanics and The Heat Equation), and it won't work on http://www.climateaudit.org/phpBB3/viewtopic.php?f=4&t=766&p=14997#p14997 . Is there any useful tools for debugging latex equations? If anyone is curious the above equation is the Euler Lagrange Equation.

 

[Dragonfall]

\mathcal is usually succeeded by {blah}. Could that be the problem?

You can use TeXnic for debugging information.

 

[John Creighto]

\mathcal is usually succeeded by {blah}. Could that be the problem?

You can use TeXnic for debugging information.

I gave it a try. No such luck though. Thanks though. I'm going to give TeXnic a try. Hopefully it will save me a lot of trouble in the future.

 

[cristo]

Try changing \text to \textrm (or something).

 

[statdad]

"\mathcal is usually succeeded by {blah}. Could that be the problem?"

No - if the argument to mathcal is longer than a single character then {} would be needed, but without them it is applied only to the next character, the L.

I copied your code and tried it in Latexit on my Macbook pro - no problem - it compiled it without a hitch, and displayed it just as you see it above. If this is indeed what it should look like, perhaps there is a code structure used here that your other software doesn't support? Or perhaps it's something so glaringly simple that we all miss it at first shot.

$$\left(\frac{\partial \mathcal L(a_1,…a_n, …;\dot a_1,..,\dot a_n, …;t)}{\partial a_i}\right) - \left(\frac{d}{dy} \frac{\partial \mathcal L(a_1,…a_n, …;\dot a_1,..,\dot a_n, …;t)}{\partial \dot a_i}\right) = 0 \quad \text{for } i = 1, \dots, n, i \neq j$$

and no, \text is designed specifically to be used inside displays like this, so we no longer have to work with those annoying little boxes to get the formatting correct. textrm would probably work too, but I don't think this is where the problem might be.

 

[cristo]

no, \text is designed specifically to be used inside displays like this, so we no longer have to work with those annoying little boxes to get the formatting correct. textrm would probably work too, but I don't think this is where the problem might be.

Well, I just ran the input in a boring tex file (i.e. something that looked like \documentclass{article}\begin{document}$$math$$\end{document}), and I got an "undefined control sequence" error for \text, which this went away with \textrm.By the way, to the OP, you should replace "..." with "\ldots".

 

[statdad]

Well, I just ran the input in a boring tex file (i.e. something that looked like \documentclass{article}\begin{document}$$math$$\end{document}), and I got an "undefined control sequence" error for \text, which this went away with \textrm.


By the way, to the OP, you should replace "..." with "\ldots".

Bingo - \text works when the amsmath package is used - if you don't have it in your preamble you get the undefined control sequence error.

I don't know how the interpreters for this site and the OPs blogs are set up, but it would seem that the default settings here load amsmath while the other sites do not.

 

[John Creighto]

By the way, to the OP, you should replace "..." with "\ldots".

Thankyou. This was the problem :)