[Tex/LaTex] Reset equation line numbers in Lyx

displaystyleequationslyxmath-modenumbering

In Lyx, how can I reset the line numbers between display-style equations?

For example, if I have the following setup:

Some text
   Line of display-style equation
   Another line of display-style equation
   A third line of the same
More text
   Line of a new display-style equation
   Another line of the same new one
Text again

and activate Math → Number Whole Formula on both equations, the line numbers are (1) (2) (3) as expected for the first equation, but (4) (5) for the second. This is unexpected. I would like the numbers to be (1) (2) (3) for the first, then (1) (2) for the second.

I tried this, adding \@addtoreset{equation}{part} to my preamble (the equations happen to be in different parts, even though that's not always true), in the hope that equation numbering rules might also apply to line numbering rules, but to no avail.

How can I achieve this?

Best Answer

You can reset the numbering of equations by adding the following to your document preamble (Document > Settings... > LaTeX preamble):

\usepackage{etoolbox}% http://ctan.org/pkg/etoolbox
\makeatletter
\let\old@start@align\start@align
\def\start@align{\setcounter{equation}{0}\old@start@align}
\makeatother

This patches the align-related macro used at the start of the environment to always reset your counter to 0 (counters are typically incremented before setting them). Your LyX display will resemble

enter image description here

but the output will be

enter image description here

Related Solutions

[Tex/LaTex] Equation numbers messed up

Looks like \numberwithin is not meant to be used the way you are trying to use it. (I'm surprised too!) The problem is that it essentially does two things:

Calls \renewcommand*\the<slave counter>{\the<master counter>.\arabic{slave counter}}
Calls \@addtoreset{<slave counter>}{<master counter>}

The second one is what change the numbering. Notice that it is "addtoreset". Which means that it will make the increment operation on the master counter trigger a reset of the slave counter. So after calling \numberwithin{equation}{section}, the trigger has been laid. And a second call of \numberwithin{equation}{chapter} does not remove the previous trigger. Therefore the equation counter will still be reset everytime the section counter increases.

So much for why it does what you see that it does. For a solution, clearly you must stop using the convenient \numberwithin command. A substitute is the \counterwithin and \counterwithout commands provided by the chngcntr package.

So you should define, in your preamble, the following commands:

\usepackage{chngcntr}

\newcommand*\startappendixeqnumbering{%
    \counterwithout{equation}{chapter}%
    \counterwithin{equation}{section}%
    \renewcommand*\theequation{\thechapter.\thesection.\arabic{equation}}}
\newcommand*\startnormaleqnumbering{%
    \counterwithout{equation}{section}%
    \counterwithin{equation}{chapter}%
    \renewcommand*\theequation{\thechapter.\arabic{equation}}}

\counterwithin{equation}{chapter}  %Set the default

And call \startappendixeqnumbering before the first appendix and \startnormaleqnumbering after the last appendix, before the start of the next chapter.

[Tex/LaTex] Numbering equations with LyX

The "proper" way to do this would, I suppose, be to turn on the numbering of the equations you want to number. You can do this by right clicking the equation and selecting Number this formula. There is also a keyboard shortcut, Alt + M N (hold down Alt, press M, release both, press N), which will work if the cursor is inside in equation.

Of course this is tedious work if you have a lot of equations, so it is better to number as you go. Either by adding a normal displayed equation and numbering as mentioned above, or inserting a numbered equation directly, with Insert --> Math --> Numbered formula.

This is also quite tedious, Ctrl+Shift+M is much easier. What one can do is to modify this shortcut to insert a numbered formula instead, or add a new shortcut for this purpose. Changing keyboard shortcuts are done in Tools --> Preferences --> Editing --> Shortcuts, see e.g. Shortcuts for Lemma, Claim, Theorem etc for details. A function you can use for such a shortcut is

command-sequence math-mode on; math-mutate equation;math-number-toggle

Again though, this doesn't help if one already has written the entire document with unnumbered equations. Then the trick mentioned in the LyX wiki, that you seem to have found, is more convenient: go to Document --> Settings --> LyX preamble and add the following two lines:

\renewcommand\[{\begin{equation}} 
\renewcommand\]{\end{equation}}

This won't add numbering of the equations within LyX, but in the PDF they will be numbered.

Best Answer

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[Tex/LaTex] Equation numbers messed up

[Tex/LaTex] Numbering equations with LyX

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