Tuesday, 22 January 2008

Lyx: equation numbering ALT+M N

LATEX is at its best when handling mathematical equations. Using LyX, you can get those perfect
equations with relatively little effort. There are two ways of entering equations. The first is to
use the menus. The “math” submenu in the “insert” menu contains everything you need. The
only problem is that it is clumsy, and only suitable for very beginning users. Far better is to
use the keyboard. The Alt-m key sequence gives you pretty much everything you need to create
equations. Let us try to create the following equation:

1. First enter the “Descriptive Math Mode” by pressing Alt-m d which starts an equation on
a separate line.
2. The terms on the left side involve fractions. A fraction is entered by typing Alt-m f (“f”
for fraction). To enter the ¶ symbol, type Alt-m p (“p” for partial). So type
Alt-m d Alt-m f Alt-m p A Alt-m p z
The takes you to the denominator field, while the leaves the fraction
and allows you to enter the next term.
3. The second term involves a subscript. This is done by typing “_”. So the second term is
entered as:
+ v_G Alt-m f Alt-m p A Alt-m p t
The “v_G” entry creates vG.

4. The third term involves superscripts. This is done by typing “^”. So the third term is
entered as follows:
+ iD Alt-m f Alt-m p^2 A Alt-m p t^2
Notice the “Alt-m p^2” and the “t^2” entries. These create the second derivitives.
5. The term on the right involves a Greek letter and vertical bars. These are entered as follows:
= Alt-m g g |A|^2 A
Here the “Alt-m g” sequence selects the Greek keyboard, where “abcde. . . ” become
“abcde. . . ”. The vertical bar is just directly typed in as seen above.
6. Finally, we want to give the equation a num
ber. By default, LyX does not number equations.
If you want to add a number to an equation, just put the cursor into the equation
and type Alt-m n. The equation number is automatically generated, and is guaranteed to be
in proper sequence, with proper respect paid to style. If you want to remove an equation
number, just type Alt-m Shift-n.
However, the only real reason to number an equation such as Eq. (1) is to refer to it in the
text. In that case, we can’t just add a number, we have to give that number a meaningful

label. This is done by placing the cursor in the equation, and typing Alt-i l, which opens
up a dialog box where you can give the name of the label, say “eq:maineq” (by default,
LyX will put “eq:” as part of an equation label to keep it from being confused with a
section label or a figure label or any other labe
l). Once you have done that, you can refer
to that equation elsewhere by typing
Eq. Alt-i r and selecting “eq:maineq”

That is pretty much it. There is much more you can do, like creating matrices, integral signs etc.
But the essence of the math mode in LyX is what we just did. But look at the result (type Alt-x
p) and see the quality of the typesetting that we have painlessly obtained. The Alt-m keyboard is
summarized below for quick reference:

Normally, equation with label will be numbered automatically.


AMK said...

Hi, how to do you link an equation reference in the text to an equation line. Thus, updating the text equation number when the actual equation number changes.

Cross UK said...

Hi Amk

When you have made your equation, just select or click on the equation, then from the toolbar select 'insert label'. A label dialog will come out, where you can give a name to your equation.
In the text area, where the equation label you want to and have inserted, will appear as the number of that equation. All are done automatically.

I am not sure is this what you mean. If not, let me know, I will be glad to help.

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